Doubt
Call us on
Email us at
Menubar
Orchids LogocloseIcon
ORCHIDS The International School

NCERT solutions for class 8 maths chapter 15 Introduction to Graphs

Download the free PDF of NCERT Solutions for Class 8 Maths Chapter 15, Introduction to Graphs, which is crucial for fostering logical and mental skills in students. Crafted by subject experts in accordance with the latest CBSE Class 8 Syllabus, these exercise-specific solutions aid students in assignments and exam preparation for the academic year 2023-24. Regular practice of Class 7 NCERT Maths Solutions is recommended to enhance problem-solving abilities, facilitating high marks in examinations.

Exercise 15.1

Question 1 :

For an experiment in Botany, two different plants, plant A and plant B, were grown under similar laboratory conditions. Their heights were measured at the end of each week for 3 weeks. The results are shown by the following graph.

Ncert solution class 8 chapter 15-3

(a) How high was Plant A after (i) 2 weeks (ii) 3 weeks?

(b) How high was Plant B after (i) 2 weeks (ii) 3 weeks?

(c) How much did Plant A grow during the 3rd week?

(d) How much did Plant B grow from the end of the 2nd week to the end of the 3rd week?

(e) During which week did Plant A grow most?

(f) During which week did Plant B grow least?

(g) Were the two plants of the same height during any week shown here? Specify.

 

Answer :

(a) (i) Plant A was 7 cm high after 2 weeks.

(ii) After 3 weeks, it was 9 cm high.

 

(b) (i) Plant B was also 7 cm high after 2 weeks.

(ii) After 3 weeks, it was 10 cm high.

 

(c) Plant A grew=9 cm–7 cm = 2 cm during 3rd week

(d) Plant B grew from end of the 2nd week to the end of the 3rdweek = 10cm–7cm= 3cm

(e) Plant A grew the highest during the second week.

(f) Plant B grew the least during first week.

(g) Yes. At the end of the second week, plants A and B were of the same height, which is 7 cm.

 


Question 2 :

The following line graph shows the yearly sales figures for a manufacturing company.

Ncert solution class 8 chapter 15-2

(a) What were the sales in (i) 2002 (ii) 2006?

(b) What were the sales in (i) 2003 (ii) 2005?

(c) Compute the difference between the sales in 2002 and 2006.

(d) In which year was there the greatest difference between the sales as compared to the previous year?

 

Answer :

(a) The sales in

(i) 2002 was Rs. 4 crores and (ii) 2006 was Rs. 8 crores

(b) The sales in

(i) 2003 was Rs. 7 crores and (ii) 2005 was Rs. 10 crores.

(c) The difference of sales in 2002 and 2006 = Rs. 8 crores–Rs. 4 crores= Rs. 4 crores

(d) In the year 2005, there was the greatest difference between the sales, and compared to its previous year, which is (Rs. 10 crores –Rs. 6 crores) = Rs. 4 crores

 


Question 3 :

A courier person cycles from a town to a neighboring suburban area to deliver a parcel to a merchant. His distance from the town at different times is shown by the following graph.

(a) What is the scale taken for the time axis?

(b) How much time did the person take for the travel?

(c) How far is the place of the merchant from the town?

(d) Did the person stop on his way? Explain.

(e) During which period did he ride fastest?

Ncert solution class 8 chapter 15-9

 

 

Answer :

(a) 4 units = 1 hour

(b) The person took 3 ½ hours for the travel.

(c) It was 22 km far from the town.

(d) Yes, this has been indicated by the horizontal part of the graph. He stayed from 10 a.m. to 10.30 a.m.

(e) He rides the fastest between 8 a.m. and 9 a.m.

 


Question 4 :

 Can there be a time-temperature graph as follows? Justify your answer.

Ncert solution class 8 chapter 15-10

 

 

Answer :

(i) It is a time-temperature graph. It is showing the increase in temperature as time increases.

(ii) It is a time-temperature graph. It is showing the decrease in temperature as time increases.

(iii) The graph figure (iii) is not possible since the temperature is increasing very rapidly, which is not possible.

(iv) It is a time-temperature graph. It is showing constant temperature.

 


Question 5 :

The following graph shows the temperature forecast and the actual temperature for each day of the week.

(a) On which days was the forecast temperature the same as the actual temperature?

(b) What was the maximum forecast temperature during the week?

(c) What was the minimum actual temperature during the week?

(d) On which day did the actual temperature differ the most from the forecast temperature?

Ncert solution class 8 chapter 15-4

 

 

Answer :

(a) On Tuesday, Friday and Sunday, the forecast temperature was same as the actual temperature.

(b) The maximum forecast temperature was 35oC.

(c) The minimum actual temperature was 15oC.

(d) The actual temperature differed the most from the forecast temperature on Thursday.

 


Question 6 :

The following graph shows the temperature of a patient in a hospital, recorded every hour.

(a) What was the patient’s temperature at 1 p.m.?

(b) When was the patient’s temperature 38.5° C?

Ncert solution class 8 chapter 15-1

(c) The patient’s temperature was the same two times during the period given. What were these two times?

(d) What was the temperature at 1.30 p.m.? How did you arrive at your answer?

(e) During which periods did the patient’s temperature show an upward trend?

 

Answer :

(a) The patient’s temperature was 36.5oC at 1 p.m.

(b) The patient’s temperature was 38.5oC at 12 noon.

(c) The patient’s temperature was same at 1 p.m. and 2p.m

(d) The temperature at 1.30 p.m. is 36.5oC.

The point between 1p.m.and 2 p.m., the x-axis is equidistant from the two points showing 1 p.m. and 2 p.m. So, it represents 1.30 p.m. Similarly, the point on the y-axis, between 360 C and 370 C, represents 36.50 C.

(e) The patient’s temperature showed an upward trend from 9 a.m. to 11 a.m. and from 2 p.m. to 3 p.m.

 


Question 7 :

Use the tables below to draw linear graphs

(a) The number of days a hillside city received snow in different years.

Ncert solution class 8 chapter 15-5

(b) Population (in thousands) of men and women in a village in different years.

Ncert solution class 8 chapter 15-6

 

 

Answer :

(a) Consider “Years” along the x-axis and “Days” along the y-axis. Using the given information, the linear graph will look like this:

Ncert solution class 8 chapter 15-7

(b) Consider “Years” along the x-axis and “No. of Men and No. of Women” along the y-axis (2 graphs). Using the given information, the linear graph will look like this:

Ncert solution class 8 chapter 15-8

 


Exercise 15.2

Question 1 :

State whether True or False. Correct those that are False.

(i) A point whose x-coordinate is zero and y-coordinate is non-zero will lie on the y-axis.

(ii) A point whose y-coordinate is zero and x-coordinate is 5 will lie on the y-axis.

(iii) The coordinates of the origin are (0, 0).

 

Answer :

i) True.

ii) False; it will lie on the x-axis.

(iii) True.

 


Question 2 :

 Draw the line passing through (2,3)and(3,2). Find the coordinates of the points at which this line meets the x-axis and y-axis.

 

Answer :

Graph for the line passes through points (2, 3) and (3, 2) is

Ncert solution class 8 chapter 15-12

The coordinates of the points at which this line meets the x-axis at (5, 0) and Y axis at (0,5).

 


Question 3 :

Write the coordinates of the vertices of each of these adjoining figures.

Ncert solution class 8 chapter 15-13

 

Answer :

We can observe three figures named as, OABC, PQRS and LMK.

Vertices of figure OABC

O (0, 0), A (2, 0), B (2, 3) and C (0, 3)

Vertices of figure PQRS

P (4, 3), Q (6, 1), R (6, 5) and S (4, 7)

Vertices of figure LMK

L (7, 7), M(10, 8) and K(10,5)

 


Question 4 :

Plot the following points on a graph sheet. Verify if they lie on a line

(a) A(4,0), B(4, 2),C(4,6), D(4, 2.5)

(b) P(1, 1), Q(2, 2), R(3,3), S(4, 4)

(c) K(2, 3), L(5, 3), M(5,5), N(2, 5)

 

Answer :

Plot all the points on the graph.

Ncert solution class 8 chapter 15-11

(a) All points, A, B, C and D, lie on a vertical line.

(b) P,Q, R and S points also make a line. It verifies that these points lie on a line.

(c) Points K, L, M and N. These points do not lie in a straight line.

 


Exercise 15.3

Question 1 :

 Draw a graph for the following.

Ncert solution class 8 chapter 15-20

 

 

Answer :

(i) Yes, it is a linear graph.

Ncert solution class 8 chapter 15-21

(ii) No, it is not a linear graph because the graph does not provide a straight line.

Ncert solution class 8 chapter 15-22

 


Question 2 :

Draw the graphs for the following tables of values, with suitable scales on the axes.

(a) Cost of apples.

Ncert solution class 8 chapter 15-14

(b) Distance travelled by car.

Ncert solution class 8 chapter 15-15

(i) How much distance did the car cover during the period 7.30 a.m. to 8 a.m.?

(ii) What was the time when the car had covered a distance of 100 km since its start?

(c) Interest on deposits for a year.

Ncert solution class 8 chapter 15-16

(i) Does the graph pass through the origin?

(ii) Use the graph to find the interest on Rs 2500 for a year.

(iii) To get an interest of Rs. 280 per year, how much money should be deposited?

 

Answer :

Mark “number of apples” on the x-axis and “cost” on the y-axis. The graph is

Ncert solution class 8 chapter 15-17

(b) Represent the “time” on the x-axis and “distance” on the y-axis.

Ncert solution class 8 chapter 15-18

(i) The car covered a distance of 20 km.

(ii) It was 7.30 am, when it covered a distance of 100 km.

(c) Represent “Deposit” on the y-axis and “simple interest” on the x-axis.

Ncert solution class 8 chapter 15-19

(i) Yes, the graph passes through the origin.

(ii) Interest on Rs. 2500 is Rs. 200 for a year.

(iii) Rs. 3500 should be deposited for the interest of Rs. 280.

 


Enquire Now

| K12 Techno Services ®

ORCHIDS - The International School | Terms | Privacy Policy | Cancellation