NCERT solutions for class 7 maths chapter 1 Integers

Withdrawal of the amount from the account is represented by a negative integer.

Then, the deposit of the amount to the account is represented by a positive integer.

From the question,

Total amount deposited in bank account by the Mohan = ₹ 2000

The total amount is withdrawn from the bank account by the Mohan = – ₹ 1642

Balance in Mohan’s account after the withdrawal = amount deposited + amount withdrawn

= ₹ 2000 + (-₹ 1642)

= ₹ 2000 – ₹ 1642

= ₹ 358

Hence, the balance in Mohan’s account after the withdrawal is ₹ 358

 

From the question,

The plane is flying at the height = 5000 m

Depth of Submarine = -1200 m

The vertical distance between plane and submarine = 5000 m – (- 1200) m

= 5000 m + 1200 m

= 6200 m

 

From the question,

The temperature on Monday at Srinagar = -5oC

The temperature on Tuesday at Srinagar has dropped by 2oC = Temperature on Monday –2oC

= -5oC – 2oC

= -7oC

The temperature on Wednesday at Srinagar rose by 4oC = Temperature on Tuesday + 4oC

= -7oC + 4oC

= -3oC

Thus, the temperature on Tuesday and Wednesday was -7oC and -3oC, respectively.

 

From the question,

Jack’s scores in five successive rounds are 25, -5, -10, 15 and 10

The total score of Jack at the end will be = 25 + (-5) + (-10) + 15 + 10

= 25 – 5 – 10 + 15 + 10

= 50 – 15

= 35

∴ Jack’s total score at the end is 35.

 

(i) Let us consider steps moved down are represented by positive integers, and steps moved up are represented by negative integers.

Initially, the monkey is sitting on the topmost step, i.e., the first step

In the 1st jump the monkey will be at step = 1 + 3 = 4 steps

In the 2nd jump the monkey will be at step = 4 + (-2) = 4 – 2 = 2 steps

In the 3rd jump the monkey will be at step = 2 + 3 = 5 steps

In the 4th jump the monkey will be at step = 5 + (-2) = 5 – 2 = 3 steps

In the 5th jump the monkey will be at step = 3 + 3 = 6 steps

In the 6th jump the monkey will be at step = 6 + (-2) = 6 – 2 = 4 steps

In the 7th jump the monkey will be at step = 4 + 3 = 7 steps

In the 8th jump the monkey will be at step = 7 + (-2) = 7 – 2 = 5 steps

In the 9th jump the monkey will be at step = 5 + 3 = 8 steps

In the 10th jump the monkey will be at step = 8 + (-2) = 8 – 2 = 6 steps

In the 11th jump the monkey will be at step = 6 + 3 = 9 steps

∴ The monkey took 11 jumps (i.e., the 9th step) to reach the water level.

(ii) Let us consider steps moved down are represented by positive integers, and then steps moved up are represented by negative integers.

Initially, the monkey is sitting on the ninth step, i.e., at the water level

In the 1st jump the monkey will be at step = 9 + (-4) = 9 – 4 = 5 steps

In the 2nd jump the monkey will be at step = 5 + 2 = 7 steps

In the 3rd jump the monkey will be at step = 7 + (-4) = 7 – 4 = 3 steps

In the 4th jump the monkey will be at step = 3 + 2 = 5 steps

In the 5th jump the monkey will be at step = 5 + (-4) = 5 – 4 = 1 step

∴ The monkey took 5 jumps to reach back to the top step, i.e., the first step.

(iii)

From the question, it is given that

If the number of steps moved down is represented by negative integers and the number of steps moved up by positive integers,

Monkey moves in part (i)

= – 3 + 2 – ……….. = – 8

Then LHS = – 3 + 2 – 3 + 2 – 3 + 2 – 3 + 2 – 3 + 2 – 3

= – 18 + 10

= – 8

RHS = -8

∴ Moves in part (i) represent that the monkey is going down 8 steps because of a negative integer.

Now,

Monkey moves in part (ii)

= 4 – 2 + ……….. = 8

Then LHS = 4 – 2 + 4 – 2 + 4

= 12 – 4

= 8

RHS = 8

∴ Moves in part (ii) represent that the monkey is going up 8 steps because of a positive integer.

 

 

 

(a) Let us take Left Hand Side (LHS) = (-8) + (-4)

= -8 – 4

= -12

Now, Right Hand Side (RHS) = (-8) – (-4)

= -8 + 4

= -4

By comparing LHS and RHS

LHS < RHS

-12 < -4

∴ (-8) + (-4) [<] (-8) – (-4)

(b) Let us take Left Hand Side (LHS) = (-3) + 7 – 19

= -3 + 7 – 19

= -22 + 7

= -15

Now, Right Hand Side (RHS) = 15 – 8 + (-9)

= 15 – 8 – 9

= 15 – 17

= -2

By comparing LHS and RHS

LHS < RHS

-15 < -2

∴ (-3) + 7 – (19) [<] 15 – 8 + (-9)

(c) Let us take Left Hand Side (LHS) = 23 – 41 + 11

= 34 – 41

= – 7

Now, Right Hand Side (RHS) = 23 – 41 – 11

= 23 – 52

= – 29

By comparing LHS and RHS

LHS > RHS

– 7 > -29

∴ 23 – 41 + 11 [>] 23 – 41 – 11

(d) Let us take Left Hand Side (LHS) = 39 + (-24) – 15

= 39 – 24 – 15

= 39 – 39

= 0

Now, Right Hand Side (RHS) = 36 + (-52) – (- 36)

= 36 – 52 + 36

= 72 – 52

= 20

By comparing LHS and RHS

LHS < RHS

0 < 20

∴ 39 + (-24) – (15) [<] 36 + (-52) – (- 36)

(e) Let us take Left Hand Side (LHS) = – 231 + 79 + 51

= – 231 + 130

= -101

Now, Right Hand Side (RHS) = – 399 + 159 + 81

= – 399 + 240

= – 159

By comparing LHS and RHS

LHS > RHS

-101 > -159

∴ – 231 + 79 + 51 [>] -399 + 159 + 81

 

(i) From the question,

a = 21 and b = 18

To verify a – (- b) = a + b

Let us take Left Hand Side (LHS) = a – (- b)

= 21 – (- 18)

= 21 + 18

= 39

Now, Right Hand Side (RHS) = a + b

= 21 + 18

= 39

By comparing LHS and RHS

LHS = RHS

39 = 39

Hence, the value of a and b is verified.

(ii) From the question,

a = 118 and b = 125

To verify a – (- b) = a + b

Let us take Left Hand Side (LHS) = a – (- b)

= 118 – (- 125)

= 118 + 125

= 243

Now, Right Hand Side (RHS) = a + b

= 118 + 125

= 243

By comparing LHS and RHS

LHS = RHS

243 = 243

Hence, the value of a and b is verified.

(iii) From the question,

a = 75 and b = 84

To verify a – (- b) = a + b

Let us take Left Hand Side (LHS) = a – (- b)

= 75 – (- 84)

= 75 + 84

= 159

Now, Right Hand Side (RHS) = a + b

= 75 + 84

= 159

By comparing LHS and RHS

LHS = RHS

159 = 159

Hence, the value of a and b is verified.

(iv) From the question,

a = 28 and b = 11

To verify a – (- b) = a + b

Let us take Left Hand Side (LHS) = a – (- b)

= 28 – (- 11)

= 28 + 11

= 39

Now, Right Hand Side (RHS) = a + b

= 28 + 11

= 39

By comparing LHS and RHS

LHS = RHS

39 = 39

Hence, the value of a and b is verified.

 

(a) By observing the number line, we can find the temperature of the cities as follows,

The temperature at Lahulspiti is -8oC

The temperature at Srinagar is -2oC

The temperature at Shimla is 5oC

The temperature at Ooty is 14oC

The temperature at Bengaluru is 22oC

(b) From the number line, we observe that,

The temperature at the hottest place, i.e. Bengaluru, is 22oC

The temperature at the coldest place, i.e., Lahulspiti, is -8oC

Temperature difference between hottest and coldest place is = 22oC – (-8oC)

= 22oC + 8oC

= 30oC

Hence, the temperature difference between the hottest and the coldest place is 30oC.

(c) From the given number line,

The temperature at Lahulspiti is -8oC

The temperature at Srinagar is -2oC

∴ The temperature difference between Lahulspiti and Srinagar is = -2oC – (8oC)

= – 2OC + 8oC

= 6oC

(d) From the given number line,

The temperature at Srinagar =-2oC

The temperature at Shimla = 5oC

The temperature of Srinagar and Shimla, taken together, is = – 2oC + 5oC

= 3oC

∴ 5oC > 3oC

So, the temperature of Srinagar and Shimla, taken together, is less than the temperature at Shimla.

Then,

3o > -2o

Hence, the temperature of Srinagar and Shimla, taken together, is not less than the temperature of Srinagar.

 

First, we consider the square (i)

By adding the numbers in each row, we get

= 5 + (- 1) + (- 4) = 5 – 1 – 4 = 5 – 5 = 0

= -5 + (-2) + 7 = – 5 – 2 + 7 = -7 + 7 = 0

= 0 + 3 + (-3) = 3 – 3 = 0

By adding the numbers in each column, we get

= 5 + (- 5) + 0 = 5 – 5 = 0

= (-1) + (-2) + 3 = -1 – 2 + 3 = -3 + 3 = 0

= -4 + 7 + (-3) = -4 + 7 – 3 = -7 + 7 = 0

By adding the numbers in diagonals, we get

= 5 + (-2) + (-3) = 5 – 2 – 3 = 5 – 5 = 0

= -4 + (-2) + 0 = – 4 – 2 = -6

Because the sum of one diagonal is not equal to zero,

(i) is not a magic square

Now, we consider the square (ii)

By adding the numbers in each row, we get

= 1 + (-10) + 0 = 1 – 10 + 0 = -9

= (-4) + (-3) + (-2) = -4 – 3 – 2 = -9

= (-6) + 4 + (-7) = -6 + 4 – 7 = -13 + 4 = -9

By adding the numbers in each column, we get

= 1 + (-4) + (-6) = 1 – 4 – 6 = 1 – 10 = -9

= (-10) + (-3) + 4 = -10 – 3 + 4 = -13 + 4

= 0 + (-2) + (-7) = 0 – 2 – 7 = -9

By adding the numbers in diagonals, we get

= 1 + (-3) + (-7) = 1 – 3 – 7 = 1 – 10 = -9

= 0 + (-3) + (-6) = 0 – 3 – 6 = -9

This (ii) square is a magic square because the sum of each row, each column and the diagonal is equal to -9.

 

From the question, it is given that

A positive integer represents the distance towards the east.

Then, the distance travelled towards the west will be represented by a negative integer.

Rita travels a distance in the east direction = 20 km

Rita travels a distance in the west direction = – 30 km

∴ Distance travelled from A = 20 + (- 30)

= 20 – 30

= -10 km

Hence, we will represent the distance travelled by Rita from point A by a negative integer, i.e., –10 km

 

From the question, it is given that

The score of team A = -40, 10, 0

Total score obtained by team A = -40 + 10 + 0

= -30

The score of team B = 10, 0, -40

Total score obtained by team B = 10 + 0 + (-40)

= 10 + 0 – 40

= -30

Thus, the score of both team A and team B is the same.

Yes, we can say that we can add integers in any order.

 

(a)   = -4 + (-3)

        = -4 – 3 … [∵ (+ × – = -)]

        = -7

(b)   = -25 – (-15)

        = – 25 + 15 … [∵ (- × – = +)]

       = -10

(c)   = 4 + (-4)

       = 4 – 4

       = 0

 

(i) Let us assume the missing integer be x,

Then,

= (-5) + (-8) = (-8) + (x)

= -5 – 8 = – 8 + x

= -13 = -8 + x

By sending -8 from RHS to LHS, it becomes 8,

= -13 + 8 = x

= x = -5

Now, substitute the x value in the blank place,

(-5) + (-8) = (-8) + (-5) … [This equation is in the form of the Commutative law of Addition].

(ii) Let us assume the missing integer be x,

Then,

= -53 + x = -53

By sending -53 from LHS to RHS, it becomes 53,

= x = -53 + 53

= x = 0

Now, substitute the x value in the blank place,

= -53 + 0 = -53 … [This equation is in the form of the closure property of addition]

(iii) Let us assume the missing integer be x,

Then,

= 17 + x = 0

By sending 17 from LHS to RHS, it becomes -17,

= x = 0 – 17

= x = -17

Now, substitute the x value in the blank place,

= 17 + (-17) = 0 … [This equation is in the form of closure property of addition]

= 17 – 17 = 0

(iv) Let us assume the missing integer be x,

Then,

= [13 + (–12)] + (x) = 13 + [(–12) + (–7)]

= [13 – 12] + (x) = 13 + [–12 –7]

= [1] + (x) = 13 + [-19]

= 1 + (x) = 13 – 19

= 1 + (x) = -6

By sending 1 from LHS to RHS, it becomes -1

= x = -6 – 1

= x = -7

Now, substitute the x value in the blank place,

= [13 + (-12)] + (-7) = 13 + [(–12) + (-7)] … [This equation is in the form of associative property of addition].

(v) Let us assume the missing integer be x,

Then,

= (-4) + [15 + (-3)] = [-4 + 15] + x

= (-4) + [15 – 3)] = [-4 + 15] + x

= (-4) + [12] = [11] + x

= 8 = 11 + x

By sending 11 from RHS to LHS, it becomes -11

= 8 – 11 = x

= x = -3

Now, substitute the x value in the blank place,

= (-4) + [15 + (-3)] = [-4 + 15] + -3 … [This equation is in the form of Associative property of Addition].

 

(a)    = (-5) – (-13)

         = -5 + 13 … [∵ (- × – = +)]

         = 8

(b)    = -25 + 20

         = -5

(c)     = -2 – (1)

         = -2 – 1

          = -3

 

The various products are,

= -1 × 5 = -5

= -1 × 4 = -4

= -1 × 3 = -3

= -1 × 2 = -2

= -1 × 1 = -1

= -1 × 0 = 0

= -1 × -1 = 1

We concluded that the product of one negative integer and one positive integer is a negative integer. Then, the product of two negative integers is a positive integer.

 

(a) We denote profit in positive integers and loss in negative integers,

From the question,

The cement company earns a profit on selling 1 bag of white cement = ₹ 8 per bag

Then,

The cement company earns a profit on selling 3000 bags of white cement = 3000 × ₹ 8

= ₹ 24000

Loss on selling 1 bag of grey cement = – ₹ 5 per bag

Then,

Loss on selling 5000 bags of grey cement = 5000 × – ₹ 5

= – ₹ 25000

Total loss or profit earned by the cement company = profit + loss

= 24000 + (-25000)

= – ₹1000

Thus, a loss of ₹ 1000 will be incurred by the company.

(b) We denote profit in positive integers and loss in negative integers,

From the question,

The cement company earns a profit on selling 1 bag of white cement = ₹ 8 per bag

Let the number of white cement bags be x.

Then,

The cement company earns a profit on selling x bags of white cement = (x) × ₹ 8

= ₹ 8x

Loss on selling 1 bag of grey cement = – ₹ 5 per bag

Then,

Loss on selling 6400 bags of grey cement = 6400 × – ₹ 5

= – ₹ 32000

According to the question,

The company must sell to have neither profit nor loss.

= Profit + loss = 0

= 8x + (-32000) =0

By sending -32000 from LHS to RHS, it becomes 32000

= 8x = 32000

= x = 32000/8

= x = 4000

Hence, the 4000 bags of white cement have neither profit nor loss.

 

(a) The given equation is in the form of the Distributive Law of Multiplication over Addition.

= a × (b + c) = (a × b) + (a × c)

Let, a = -48, b = 26, c = -36

Now,

= 26 × (– 48) + (– 48) × (–36)

= -48 × (26 + (-36)

= -48 × (26 – 36)

= -48 × (-10)

= 480 … [∵ (- × – = +)

(b) The given equation is in the form of the Commutative Law of Multiplication.

= a × b = b × a

Then,

= 8 × [53 × (-125)]

= 8 × [(-125) × 53]

= [8 × (-125)] × 53

= [-1000] × 53

= – 53000

(c) The given equation is in the form of the Commutative Law of Multiplication.

= a × b = b × a

Then,

= 15 × [(–25) × (– 4)] × (–10)

= 15 × [100] × (–10)

= 15 × [-1000]

= – 15000

(d) The given equation is in the form of the Distributive Law of Multiplication over Addition.

= a × (b + c) = (a × b) + (a × c)

= (-41) × (100 + 2)

= (-41) × 100 + (-41) × 2

= – 4100 – 82

= – 4182

(e) The given equation is in the form of the Distributive Law of Multiplication over Addition.

= a × (b + c) = (a × b) + (a × c)

= 625 × [(-35) + (-65)]

= 625 × [-100]

= – 62500

(f)

The given equation is in the form of the Distributive Law of Multiplication over Subtraction.

= a × (b – c) = (a × b) – (a × c)

= (7 × 50) – (7 × 2)

= 350 – 14

= 336

(g) The given equation is in the form of the Distributive Law of Multiplication over Addition.

= a × (b + c) = (a × b) + (a × c)

= (-17) × [-30 + 1]

= [(-17) × (-30)] + [(-17) × 1]

= [510] + [-17]

= 493

(h) The given equation is in the form of the Distributive Law of Multiplication over Addition.

= a × (b + c) = (a × b) + (a × c)

= (57 × 19) + (57 × 1)

= 57 [19 + 1]

= 57 × 20

= 1140

 

(i)  = (-1) × a = -a

Because when we multiply any integer a with -1, then we get the additive inverse of that integer.

(ii)  (a)

Now, multiply -22 with (-1), and we get

= -22 × (-1)

= 22

Because when we multiply integer -22 with -1, then we get the additive inverse of that integer.

(b)  Now, multiply 37 with (-1), and we get

= 37 × (-1)

= -37

Because when we multiply integer 37 with -1, then we get the additive inverse of that integer.

(c) Now, multiply 0 by (-1), and we get

= 0 × (-1)

= 0

Because the product of negative integers and zero gives zero only.

 

(a) From the given equation,

Let us consider the Left Hand Side (LHS) first = 18 × [7 + (–3)]

= 18 × [7 – 3]

= 18 × 4

= 72

Now, consider the Right Hand Side (RHS) = [18 × 7] + [18 × (–3)]

= [126] + [-54]

= 126 – 54

= 72

By comparing LHS and RHS,

72 = 72

LHS = RHS

Hence, the given equation is verified.

(b) From the given equation,

Let us consider the Left Hand Side (LHS) first = (–21) × [(– 4) + (– 6)]

= (-21) × [-4 – 6]

= (-21) × [-10]

= 210

Now, consider the Right Hand Side (RHS) = [(–21) × (– 4)] + [(–21) × (– 6)]

= [84] + [126]

= 210

By comparing LHS and RHS,

210 = 210

LHS = RHS

Hence, the given equation is verified.

 

(a) By the rule of multiplication of integers,

= 3 × (-1)

= -3 … [∵ (+ × – = -)]

(b) By the rule of multiplication of integers,

= (-1) × 225

= -225 … [∵ (- × + = -)]

(c) By the rule of multiplication of integers,

= (-21) × (-30)

= 630 … [∵ (- × – = +)]

(d)

By the rule of multiplication of integers,

= (-316) × (-1)

= 316 … [∵ (- × – = +)]

(e) By the rule of multiplication of integers,

= (–15) × 0 × (–18)

= 0

∵ If any integer is multiplied by zero, the answer is zero itself.

(f) By the rule of multiplication of integers,

= (–12) × (-11) × (10)

First, multiply the two numbers having the same sign,

= 132 × 10 … [∵ (- × – = +)]

= 1320

(g) By the rule of multiplication of integers,

= 9 × (-3) × (-6)

First, multiply the two numbers having the same sign,

= 9 × 18 … [∵ (- × – = +)]

= 162

(h) By the rule of multiplication of integers,

= (-18) × (-5) × (-4)

First, multiply the two numbers having the same sign,

= 90 × -4 … [∵ (- × – = +)]

= – 360 … [∵ (+ × – = -)]

(i) By the rule of multiplication of integers,

= [(–1) × (–2)] × [(–3) × 4]

= 2 × (-12) … [∵ (- × – = +), (- × + = -)]

= – 24

(j) By the rule of multiplication of integers,

= [(–3) × (–6)] × [(–2) × (–1)]

First, multiply the two numbers having the same sign,

= 18 × 2 … [∵ (- × – = +)

= 36

 

(i) From the question,

Marks awarded for 1 correct answer = 5

Then,

Total marks awarded for 4 correct answer = 4 × 5 = 20

Marks awarded for 1 wrong answer = -2

Then,

Total marks awarded for 6 wrong answer = 6 × -2 = -12

∴ Total score obtained by Mohan = 20 + (-12)

= 20 – 12

= 8

(ii) From the question,

Marks awarded for 1 correct answer = 5

Then,

Total marks awarded for 5 correct answer = 5 × 5 = 25

Marks awarded for 1 wrong answer = -2

Then,

Total marks awarded for 5 wrong answer = 5 × -2 = -10

∴ Total score obtained by Reshma = 25 + (-10)

= 25 – 10

= 15

(iii) From the question,

Marks awarded for 1 correct answer = 5

Then,

Total marks awarded for 2 correct answer = 2 × 5 = 10

Marks awarded for 1 wrong answer = -2

Then,

Total marks awarded for 5 wrong answer = 5 × -2 = -10

Marks awarded for questions not attempted is = 0

∴ Total score obtained by Heena = 10 + (-10)

= 10 – 10

= 0

 

From the question, it is given that

Let us take the lowered temperature as negative,

Initial temperature = 40oC

Change in temperature per hour = -5oC

Change in temperature after 10 hours = (-5) × 10 = -50oC

∴ The final room temperature after 10 hours of freezing process = 40oC + (-50oC)

= -10oC

 

(a) Let us assume the missing integer be x,

Then,

= (–3) × (x) = 27

= x = – (27/3)

= x = -9

Let us substitute the value of x in the place of blank,

= (–3) × (-9) = 27 … [∵ (- × – = +)]

(b) Let us assume the missing integer be x,

Then,

= (5) × (x) = -35

= x = – (-35/5)

= x = -7

Let us substitute the value of x in the place of blank,

= (5) × (-7) = -35 … [∵ (+ × – = -)]

(c) Let us assume the missing integer be x,

Then,

= (x) × (-8) = -56

= x = (-56/-8)

= x = 7

Let us substitute the value of x in the place of blank,

= (7) × (-8) = -56 … [∵ (+ × – = -)]

(d) Let us assume the missing integer be x,

Then,

= (x) × (-12) = 132

= x = – (132/12)

= x = – 11

Let us substitute the value of x in the place of blank,

= (–11) × (-12) = 132 … [∵ (- × – = +)]

From the question,

Marks awarded for 1 correct answer = +3

Marks awarded for 1 wrong answer = -2

(i) Radhika scored 20 marks

Then,

Total marks awarded for 12 correct answers = 12 × 3 = 36

Marks awarded for incorrect answers = Total score – Total marks awarded for 12 correct

Answers

= 20 – 36

= – 16

So, the number of incorrect answers made by Radhika = (-16) ÷ (-2)

= 8

(ii) Mohini scored -5 marks

Then,

Total marks awarded for 7 correct answers = 7 × 3 = 21

Marks awarded for incorrect answers = Total score – Total marks awarded for 12 correct

Answers

= – 5 – 21

= – 26

So, the number of incorrect answers made by Mohini = (-26) ÷ (-2)

= 13

 

From the question,

The initial height of the elevator = 10 m

The final depth of the elevator = – 350 m … [∵distance descended is denoted by a negative

integer]

The total distance to descended by the elevator = (-350) – (10)

= – 360 m

Then,

Time taken by the elevator to descend -6 m = 1 min

So, the time taken by the elevator to descend – 360 m = (-360) ÷ (-6)

= 60 minutes

= 1 hour

 

 

 

(a)  = (-30) ÷ 10

       = – 3

When we divide a negative integer by a positive integer, we first divide them as whole numbers and then put the minus sign (-) before the quotient.

(b)  = (50) ÷ (-5)

       = – 10

When we divide a positive integer by a negative integer, we first divide them as whole numbers and then put the minus sign (-) before the quotient.

(c)  = (-36) ÷ (-9)

       = 4

When we divide a negative integer by a negative integer, we first divide them as whole numbers and then put the positive sign (+) before the quotient.

(d)  = (–49) ÷ 49

       = – 1

When we divide a negative integer by a positive integer, we first divide them as whole numbers and then put the minus sign (-) before the quotient.

(e)  = 13 ÷ [(-2) + 1]

       = 13 ÷ (-1)

       = – 13

When we divide a positive integer by a negative integer, we first divide them as whole numbers and then put the minus sign (-) before the quotient.

(f)  = 0 ÷ (-12)

       = 0

When we divide zero by a negative integer gives zero.

(g)  = (–31) ÷ [(–30) + (–1)]

       = (-31) ÷ [-30 – 1]

       = (-31) ÷ (-31)

       = 1

When we divide a negative integer by a negative integer, we first divide them as whole numbers and then put the positive sign (+) before the quotient.

(h) First, we have to solve the integers within the bracket,

= [(–36) ÷ 12]

= (–36) ÷ 12

= – 3

Then,

= (-3) ÷ 3

= -1

When we divide a negative integer by a positive integer, we first divide them as whole numbers and then put the minus sign (-) before the quotient.

(i) The given question can be written as,

= [-1] ÷ [-1]

= 1

When we divide a negative integer by a negative integer, we first divide them as whole numbers and then put the positive sign (+) before the quotient.

 

(a) From the question, a ÷ (b + c) ≠ (a ÷ b) + (a ÷ c)

Given, a = 12, b = – 4, c = 2

Now, consider LHS = a ÷ (b + c)

= 12 ÷ (-4 + 2)

= 12 ÷ (-2)

= -6

When we divide a positive integer by a negative integer, we first divide them as whole numbers and then put the minus sign (-) before the quotient.

Then, consider RHS = (a ÷ b) + (a ÷ c)

= (12 ÷ (-4)) + (12 ÷ 2)

= (-3) + (6)

= 3

By comparing LHS and RHS

= -6 ≠ 3

= LHS ≠ RHS

Hence, the given values are verified.

(b) From the question, a ÷ (b + c) ≠ (a ÷ b) + (a ÷ c)

Given, a = (-10), b = 1, c = 1

Now, consider LHS = a ÷ (b + c)

= (-10) ÷ (1 + 1)

= (-10) ÷ (2)

= -5

When we divide a negative integer by a positive integer, we first divide them as whole numbers and then put the minus sign (-) before the quotient.

Then, consider RHS = (a ÷ b) + (a ÷ c)

= ((-10) ÷ (1)) + ((-10) ÷ 1)

= (-10) + (-10)

= -10 – 10

= -20

By comparing LHS and RHS

= -5 ≠ -20

= LHS ≠ RHS

Hence, the given values are verified.

 

(a) Let us assume the missing integer is x,

Then,

= 369 ÷ x = 369

= x = (369/369)

= x = 1

Now, put the valve of x in the blank.

= 369 ÷ 1 = 369

(b) Let us assume the missing integer is x,

Then,

= (-75) ÷ x = -1

= x = (-75/-1)

= x = 75

Now, put the valve of x in the blank.

= (-75) ÷ 75 = -1

(c) Let us assume the missing integer is x,

Then,

= (-206) ÷ x = 1

= x = (-206/1)

= x = -206

Now, put the valve of x in the blank.

= (-206) ÷ (-206) = 1

(d) Let us assume the missing integer is x,

Then,

= (-87) ÷ x = 87

= x = (-87)/87

= x = -1

Now, put the valve of x in the blank.

= (-87) ÷ (-1) = 87

(e) Let us assume the missing integer is x,

Then,

= (x) ÷ 1 = -87

= x = (-87) × 1

= x = -87

Now, put the valve of x in the blank.

= (-87) ÷ 1 = -87

(f) Let us assume the missing integer is x,

Then,

= (x) ÷ 48 = -1

= x = (-1) × 48

= x = -48

Now, put the valve of x in the blank.

= (-48) ÷ 48 = -1

(g) Let us assume the missing integer is x,

Then,

= 20 ÷ x = -2

= x = (20)/ (-2)

= x = -10

Now, put the valve of x in the blank.

= (20) ÷ (-10) = -2

(h) Let us assume the missing integer is x,

Then,

= (x) ÷ 4 = -3

= x = (-3) × 4

= x = -12

Now, put the valve of x in the blank.

= (-12) ÷ 4 = -3

 

(i) (15, -5)

Because, 15 ÷ (–5) = (–3)

(ii) (-15, 5)

Because, (-15) ÷ (5) = (–3)

(iii) (18, -6)

Because, 18 ÷ (–6) = (–3)

(iv) (-18, 6)

Because, (-18) ÷ 6 = (–3)

(v) (21, -7)

Because, 21 ÷ (–7) = (–3)

 

From the question, given that,

The temperature at the beginning, i.e. at 12 noon = 10oC

Rate of change of temperature = – 2oC per hour

Then,

Temperature at 1 p.m. = 10 + (-2) = 10 – 2 = 8oC

Temperature at 2 p.m. = 8 + (-2) = 8 – 2 = 6oC

Temperature at 3 p.m. = 6 + (-2) = 6 – 2 = 4oC

Temperature at 4 p.m. = 4 + (-2) = 4 – 2 = 2oC

Temperature at 5 p.m. = 2 + (-2) = 2 – 2 = 0oC

Temperature at 6 p.m. = 0 + (-2) = 0 – 2 = -2oC

Temperature at 7 p.m. = -2 + (-2) = -2 -2 = -4oC

Temperature at 8 p.m. = -4 + (-2) = -4 – 2 = -6oC

Temperature at 9 p.m. = -6 + (-2) = -6 – 2 = -8oC

∴ At 9 p.m., the temperature will be 8oC below zero

Then,

The temperature at midnight, i.e. at 12 a.m.

Change in temperature in 12 hours = -2oC × 12 = – 24oC

So, at midnight temperature will be = 10 + (-24)

= – 14oC

So, at midnight temperature will be 14oC below 0.