Subtraction Within 20
In this article, we will be learning subtraction within 20. Let’s start with a recap!
Subtraction within 10
Example:
James had some paper clips. He lost some of them. How many paper clips did James have left?
He had __________ paper clips left.
Answer:
4
Explanation:
Count the total number of paper clips and subtract the number of paper clips that are crossed out. We get:
Question 1:
Rachel had 8 bottles of water. She gave away 5 bottles of water. How many bottles of water does Rachel have left?
- 1
- 2
- 3
- 13
Answer:
(3) 3
Explanation:
Question 2:
There are 10 ducks. 2 ducks are in the pond. How many of them are not in the pond?
Answer:
(4) 8
Explanation:
Question 3:
Mr Tan has 10 pens. He gives away 3 pens. How many pens does he have left?
- 6
- 7
- 8
- 13
Answer:
(2) 7
Explanation:
Subtraction with 20 by subtracting the ones first
Example:
Nina had 17 pencils. She lost 6 pencils. How many pencils did she have left?
Nina has __________ pencils left.
Answer:
11
Explanation:
Split 17 into 10 and 7. Subtract 6 from 7. Add the answer to 10.
Step 1:
\(17 = 10 + 7\)
Step 2:
Subtract the ones.
Step 3:
\(\begin{align} 7 – 6 &= 1 \\ 10 + 1 &= 11 \end{align}\)
Question 1:
Complete the equation.
- 13
- 14
- 15
- 16
Answer:
(3) 15
Explanation:
Split 18 into 10 and 8. Subtract 3 from 8. Add the answer to 10.
Step 1:
\(18 = 10 + 8\)
Step 2:
Subtract the ones.
Step 3:
\(\begin{align} 8 – 3 &= 5 \\ 10 + 5 &= 15 \end{align} \)
Question 2:
Complete the equation.
- 13
- 15
- 16
- 17
Answer:
(4) 17
Explanation:
Split 19 into 10 and 9. Subtract 2 from 9. Add the answer to 10.
Step 1:
\(19 = 10 + 9\)
Step 2:
Subtract the ones.
Step 3:
\(\begin{align} 9 – 2 &= 7 \\ 10 + 7 &= 17 \end{align}\)
Subtraction with 20 by subtracting from 10 first
Example:
Amy had 16 buttons. She gave 8 buttons to her sister. How many buttons did Amy have left?
Answer:
8
Explanation:
Split 16 into 10 and 6. Subtract 8 from 10. Add the answer to 6.
Step 1:
\(16 = 6 + 10\)
Step 2:
Subtract from 10 first.
Step 3:
\(\begin{align} 10 - 8 &= 2 \\ 6 + 2 &= 8 \end{align} \)
Question 1:
Fill in the blank with the correct answer.
\(13 - 5 =\) __________
- 8
- 9
- 12
- 18
Answer:
(1) 8
Explanation:
Step 1:
\(13 = 10 + 3\)
Step 2:
Subtract from 10.
Step 3:
\(\begin{align} 10 - 5 &= 5 \\ 5 + 3 &= 8 \end{align}\)
Question 2:
Fill in the blank with the correct answer:
\(20 - 2 =\) __________
- 8
- 10
- 12
- 18
Answer:
(4) 18
Explanation:
Step 1:
\(20 = 10 + 10\)
Step 2:
Subtract from 10.
Step 3:
\(\begin{align} 10 - 2 &= 8 \\ 8 + 10 &= 18 \end{align}\)
Question 3:
Fill in the blank:
\(17 - 9 =\) __________
- 7
- 8
- 9
- 10
Answer:
(2) 8
Explanation:
Step 1:
\(17 = 10 + 7\)
Step 2:
Subtract from 10.
Step 3:
\(\begin{align} 10 - 9 &= 1 \\ 1 + 7 &= 8 \end{align}\)
Question 4:
Which of the following subtraction equations best represents the diagram below?
- \(19 - 6 = 12\)
- \(19 - 6 = 13\)
- \(20 - 6 = 13\)
- \(20 - 6 = 14\)
Answer:
(2) \(19 - 6 = 13\)
Explanation:
Identify the total number of cupcakes and subtract the 6 cupcakes that are crossed out.
Step 1:
\(19 = 10 + 9\)
Step 2:
Subtract from 10.
Step 3:
\(\begin{align} 10 - 6 &= 4 \\ 4 + 9 &= 13 \end{align}\)
Question 5:
Which of the following equations best represents the diagram below?
- \(13 + 2 = 5\)
- \(13 - 2 = 11\)
- \(13 - 3 = 10\)
- \(13 - 10 = 3\)
Answer:
(2) \(13 - 2 = 11\)
Explanation:
Identify the total number of pumpkins and subtract the 2 pumpkins that are crossed out.
Step 1:
\(13 = 10 + 3\)
Step 2:
Subtract from 10.
Step 3:
\(\begin{align} 10 - 2 &= 8 \\ 8 + 3 &= 11 \end{align}\)
Question 6:
Which of the following equations best represents the diagram below?
- \(10 - 4 = 6\)
- \(4 + 6 = 10\)
- \(12 - 4 = 8\)
- \(6 + 6 = 12\)
Answer:
(3) \(12 - 4 = 8\)
Explanation:
Identify the total number of birds and subtract the 4 birds that are crossed out.
Step 1:
\(12 = 10 + 2\)
Step 2:
Subtract from 10 first.
Step 3:
\(\begin{align} 10 - 4 &= 6 \\ 6 + 2 &= 8 \end{align}\)
Question 7:
There were 17 apples. Tom ate 3 of them. How many apples are left now?
- \(14 - 3 = 11\)
- \(14 - 4 = 10\)
- \(17 - 4 = 13\)
- \(17 - 3 = 14\)
Answer:
(4) \(17 - 3 = 14\)
Explanation:
Identify the total number of apples and subtract the 3 apples that were eaten.
Step 1:
\(17 = 10 + 7\)
Step 2:
Subtract from 10 first.
Step 3:
\(\begin{align} 10 - 3 &= 7 \\ 7 + 7 &= 14 \end{align} \)
Question 8:
Which of the following is equal to 7?
Answer:
(4) \(15 - 8 = 7\)
Explanation:
- \(20 - 3 = 17\)
- \(19 - 7 = 12\)
- \(18 - 3 = 15\)
- \(15 - 8 = 7\)
Question 9:
Which of the following is not equal to 11?
Answer:
(2) \(16 - 6 = 10\)
Explanation:
- \(10 + 1 = 11\)
- \(16 - 6 = 10\)
- \(13 - 2 = 11\)
- \(9 + 2 = 11\)
Question 10:
Which of the following number sentences is correct?
Answer:
(2) \(13 - 8 = 5\)
Explanation:
- \(10 - 7 = 3 \quad \text{ (wrong)}\)
- \(13 - 8 = 5 \quad\text{ (correct)}\)
- \(19 - 6 = 13 \quad\text{(wrong)}\)
- \(12 - 8 = 4 \quad\text{ (correct)}\)
Question 11:
Which of the following number sentences has the greatest answer?
Answer:
(2) \(16 - 3 = 13\)
Explanation:
- \(14 - 7 = 7\)
- \(16 - 3 = 13\)
- \(17 - 8 = 9\)
- \(20 - 9 = 11\)
Out of all the answers, 13 is the greatest.
In this article, we have learnt
- Subtraction Within 20
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