Operations on Numbers
Subtraction
We use subtraction to find the difference between numbers or when we take out/away some objects and want to find out remaining objects.
Example:
Suppose we have 5 mangoes, and we cut and eat 3 mangoes. To find the number of remaining mangoes, we need to do subtraction.
- In subtraction, we take away part of some amount.
- In subtraction, we subtract the smaller number from the bigger one.
- We subtract numbers using the symbol ‘-’, called ‘minus’.
Representation:
- We do subtraction horizontally as well as vertically.
- The larger number is called the minuend.
- The smaller number is called the subtrahend.
- The resultant number is called the Difference.
Read as: 9 minus 5 is equal to 4.
Subtraction of one-digit numbers
We can do subtraction in so many ways.
- By using fingers
- By using counters
- By using a number line
- Do mentally
We can use our hand fingers to do the subtraction. Let’s see.
Nisha has eight chocolates. She gives 3 chocolates to Sameer. Now, we need to find Nisha’s remaining number of chocolates.
First method:
Step 1: For eight chocolates open eight fingers. Step 2: To subtract three chocolates close three fingers from the open fingers. Step 3: Now count all the open fingers together. So, we got the number 5. Nisha has 5 chocolates remaining. Second method:
For subtracting 3 from 8, count the numbers after the number 3 to the number 8 and open the
fingers as well.
We got 5 fingers. So, the correct answer is 5 chocolates. Counters: In this method, we draw counters to represent numbers. Each
counter (object or shape) represents a number. Example: Question: 4-1= ? Answer: Step 1: For the number 4 draw four circles. Step 2: To subtract 1 cross the one circle. Now, count the remaining circles. There are 3 circles remaining. So, the correct answer is 4-1= 3 Number line: A straight line on which numbers are placed at the same
distance and in the correct order. Numbers are placed from left to right. Example: Question: 10-6= ? Answer:Draw a line and mark the numbers to 10 or more. Now, to subtract 6 from 10, move six steps backward to the left side from 10. You will reach at 4. So, the correct answer is: 10-6= 4
We can do subtraction by counting mentally. Example: Question: 7-3= ? Answer:Think about the number 7. Count 3 steps backward from 7. You will get 4. So, 7 – 3 = 4.
Subtraction Facts
- When we subtract 0 from a number, the answer is the number itself.
- When we subtract 1 from a number, the answer is the number that comes just before the minuend.
1 – 0 = 1, 5 – 0 = 5, 9 – 0 = 9
5 -1 = 4, 7 – 1 = 6, 9 – 1 =
Missing numerals in subtraction:
Type 1:
Here, we can take any two numbers whose difference is 5.
6-1=5
7-2=5
8-3=5
There are so many possible answers for this question.
Type 2:
Here, we need to find the number which difference from 2 is 3.
Add the numbers 2 and 3.
2+3=5
So, the correct answer is:
Word Problems
Step 1: Identify the numbers in the word problem which need to be subtracted.
Step 2: Write the word problem in the form of subtraction sentence.
Step 3: Do the subtraction and find out the difference.
Example:Question: 7 sparrows were sitting on a tree. 6 sparrows flew away. How many sparrows were now sitting on the tree?
Answer: The numbers to be subtracted are 7 and 6.
Therefore, only 1 sparrow sitting on the tree.