Math 1A Singapore-Methods of Subtraction-Chapter 4.2
Methods of Subtraction
Follow the below number sentences to understand the methods
of subtraction.
(a)
6 – 2 = 4
6 – 4 = 2
6
(b)
6 – 1 = 5
6 – 5 = 1
6
6 – 6 = 0
6 – 0 = 6
6
(d)
6 – 3 = 3
6
1. [as per workbook exercise 24 and textbook]
(a) There are 7 bats in a box. Take away 2 bats. There will
be ___ bats left.
Solution:
7
7 – 2 = 5
There will be 5 bats left.
Answer: 5
(b) There are 6 balloons. John buys 2 balloons. How many
balloons are left.
Solution:
6
6 – 2 = 4
4 balloons are left.
Answer: 4
(c) I have 6 bottles of milk. I give away 4 bottles. There
are ___ bottles left.
Solution:
6
6 – 4 = 2
There are 2 bottles left.
(d) There are 8 hats. 3 are big hats. The rest are small
hats. There are ___ small hats.
Solution:
8
8 – 3 = 5
There are 5 small hats.
Answer: 5
(e) I buy 10 cup cakes. I put 4 (four) of them on a plate.
The rest are in the box. There are ___ cup cakes in the box.
Solution:
10
10 – 4 = 6
There are 6 (six) cup cakes in the box.
2. There are 8 dolls altogether. 5 dolls belong to Morgan.
The rest belong to Emily. How many dolls does Emily have?
Solution:
8
8 – 5 = 3
Emily has 3 dolls.
Answer: 3
3. Complete the number sentences.
(a) 8 – 2 = ___
(b) 7 – 4 = ___
Solution:
(a)
8
So, 8 – 2
= 6
(b)
7
So, 7 – 4
= 3
Workbook Exercise 23 (1)
Fill in the missing numbers.
(a)
5 – 2 = ▢
5
Solution:
5 – 2 = 3
5
(b)
4 – 1 = ▢
▢
Solution:
4 – 1 = 3
4
(c)
6 – 6 = ▢
▢
Solution:
6 – 6 = 0
6
(d)
9 – 7 = ▢
▢
Solution:
9 – 7 = 2
9
Workbook Exercise 23 (2)
(a) 8 – 4 = ? 7 – 4 = ?
Answer:
8 – 4 = 4
7 – 4 = 3
(b) 10 – 4 = ? 6 – 3 = ?
Answer:
10 – 4 = 6
6 – 3 = 3
(c) 9 – 2 = ? 8 – 2 = ?
Answer:
9 – 2 = 7
8 – 2 = 6
4. Complete the number sentences.
(a)
3 + 2 = ▢ 5
– 2 = ▢
2 + 3 = ▢ 5 – 3 = ▢
Solution:
3 + 2 = 5. 5 – 2 = 3.
2 + 3 = 5. 5 – 3 = 2.
(b)
7 + 2 =▢ 9 – 2 = ▢
2 + 7 =▢ 9 – 7 = ▢
Solution:
7 + 2 = 9. 9
– 2 = 7.
2 + 7 = 9. 9
– 7 = 2.
Workbook Exercise 25(1):
(a)
5 + 1 =
▢ 1 + 5 = ▢
6 – 5 = ▢ 6 – 1 = ▢
Solution:
5 + 1 = 6. 1
+ 5 = 6.
6 – 5 = 1. 6 – 1 = 5.
(b)
4 + 3 = ▢ 3 + 4 = ▢
7 – 4 = ▢ 7 – 3 = ▢
Solution:
4 + 3 = 7. 3 + 4 = 7.
7 – 4 = 3. 7 – 3 = 4.
(c)
3 + 2 = ▢ 2 + 3 = ▢
5 – 2 = ▢ 5 – 3 = ▢
Solution:
3 + 2 = 5. 2 + 3 = 5.
5 – 2 = 3. 5 – 3 = 2.
Workbook Exercise 26(1):
Write ‘+’ or ‘-’ in each ⚪
3 ⚪ 1 = 2 2 ⚪ 2 = 0
3 ⚪
2 = 5 5 ⚪ 1 = 4
4 ⚪
3 = 1 1 ⚪ 3 = 4
Solution:
3 – 1 = 2. 2 – 2 = 0.
3 + 2 =5. 5 – 1 = 4.
4 – 3 =1. 1 + 3 = 4.
Workbook Exercise 26(2):
Use the numbers and signs to write a number sentence.
(a) 3, 10, 7, =, -
(b) 3, 7, 4, =, +
(c) 6, 6, 0, =, +
(d) 7, 9, 2, =, -
(e) 5, 3, 8, =, -
Solution:
(a)
10 – 7 = 3
10 – 3 = 7
(b)
3 + 4 = 7
4 + 3 = 7
(c)
0 + 6 = 6
6 + 0 = 6
(d)
9 – 7 = 2
9 – 2 = 7
(e)
8 – 5 = 3
8 – 3 = 5
5. Subtract 1 from 5.
Solution:
5 – 1 = 4
[1,2,3,4,5,6,..
Begin with 5 and count backwards 1 step: 4
Then we will get 4.
So, 5 – 1
= 4]
6. Subtract 2 from 7.
Solution:
7 – 2 = 5
[1,2,3,4,5,6,7,8..
Begin with 7 and count backward 2 steps: 6, 5
Then we will get 5.
So, 7 – 2 =
5]
7. Subtract 3 from 10.
Solution:
10 – 3 = 7
[5,6,7,8,9,10,….
Begin with 10 and count backward 3 steps: 9, 8, 7.
Then we will get 7.
So, 10 – 3 =
7]
8. Complete the subtraction sentence.
(a)
3 – 0 = ▢
5 – 0 = ▢
8 – 0 = ▢
Solution:
3 – 0 = 3
5 – 0 = 5
8 – 0 = 8
(b)
4 – 1 = ▢
7 – 1 = ▢
9 – 1 = ▢
Solution:
4 – 1 = 3
7 – 1 = 6
9 – 1 = 8
(c)
5 – 2 = ▢
6 – 2 = ▢
10 – 2 = ▢
Solution:
5 – 2 = 3
6 – 2 = 4
10 – 2 = 8
(d)
5 – 3 = ▢
8 – 3 = ▢
9 – 3 = ▢
Solution:
5 – 3 = 2
8 – 3 = 5
9 – 3 = 6
9. Complete the subtraction sentences.
(a)
5 – 5 = ▢
5 – 4 = ▢
5 – 3 = ▢
Solution:
5 – 5 = 0
5 – 4 = 1
5 – 3 = 2
(b)
9 – 9 = ▢
9 – 8 = ▢
9 – 7 = ▢
Solution:
9 – 9 = 0
9 – 8 = 1
9 – 7 = 2
(c)
3 – 2 = ▢
6 – 5 = ▢
9 – 8 = ▢
Solution:
3 – 2 = 1
6 – 5 = 1
9 – 8 = 1
(d)
6 – 4 = ▢
7 – 5 = ▢
8 – 6 = ▢
Solution:
6 – 4 = 2
7 – 5 = 2
8 – 6 = 2
10. Subtract 6 from 10.
Solution:
6 and 4 make 10.
10
So, 10 – 6
= 4.
11. Complete the subtraction sentences.
(a) 10 – 3 = ▢ (b) 10 – 5 = ▢
(c) 10 – 8 = ▢ (d) 10 – 9 = ▢
Solution:
(a) 10 – 3
= 7. (b) 10 – 5 = 5.
(c) 10 – 8
= 2. (d) 10 – 9 = 1.