Addition Within 20
Addition within 20 means adding numbers where the sum can go up to 20. We build on what we learned in addition within 10.
Strategies like counting on, making 10, and using doubles help solve these problems quickly.
What is Addition Within 20 - Class 1 Maths (Addition (Grade 1))?
Addition within 20 includes all problems where the answer is between 0 and 20. Examples: 8 + 5 = 13, 9 + 9 = 18, 7 + 6 = 13.
The best strategy for adding within 20 is make a 10 first, then add what is left.
Solved Examples
Example 1: 8 + 5
Question: What is 8 + 5?
Think:
- 8 needs 2 more to make 10
- Break 5 into 2 + 3
- 8 + 2 = 10, then 10 + 3 = 13
Answer: 8 + 5 = 13.
Example 2: 9 + 7
Question: What is 9 + 7?
Think:
- 9 needs 1 to make 10
- Break 7 into 1 + 6
- 9 + 1 = 10, then 10 + 6 = 16
Answer: 9 + 7 = 16.
Example 3: Counting On from 12
Question: What is 12 + 3?
Think:
- Start at 12
- Count on 3: 13, 14, 15
Answer: 12 + 3 = 15.
Example 4: Ria's Stickers
Question: Ria has 11 stickers. She buys 6 more. How many stickers?
Think:
- 11 + 6: Start at 11, count on 6: 12, 13, 14, 15, 16, 17
Answer: Ria has 17 stickers.
Example 5: 7 + 8
Question: What is 7 + 8?
Think:
- 7 needs 3 to make 10
- Break 8 into 3 + 5
- 7 + 3 = 10, then 10 + 5 = 15
Answer: 7 + 8 = 15.
Example 6: 10 + 9
Question: What is 10 + 9?
Think:
- 10 + 9 is easy — just put 9 in the ones place
- 1 ten + 9 ones = 19
Answer: 10 + 9 = 19.
Example 7: Aman's Cricket Runs
Question: Aman scored 8 runs in the first over and 6 runs in the second over. Total runs?
Think:
- 8 + 6: 8 + 2 = 10, 10 + 4 = 14
Answer: Aman scored 14 runs.
Key Points to Remember
- Addition within 20 has sums from 0 to 20.
- Make a 10 strategy: add to the bigger number to reach 10, then add what is left.
- Adding 10 + something is easy: 10 + 4 = 14, 10 + 8 = 18.
- Doubles help: 6+6=12, 7+7=14, 8+8=16, 9+9=18.
- Count on works for small additions: 14 + 2 → count 15, 16.
Practice Problems
- What is 9 + 6?
- What is 7 + 7?
- Priya has 13 beads and gets 4 more. How many now?
- Find the sum: 8 + 9.
- What is 10 + 10?
- Kavi has 6 red marbles and 8 blue marbles. How many marbles in total?
Frequently Asked Questions
Q1. What is addition within 20?
It is adding two numbers where the answer is 20 or less. Examples include 8+5=13 and 9+9=18.
Q2. What is the 'make a 10' strategy?
Break one number into parts so that one part makes 10 with the other number. For example, 8+5: take 2 from 5 to make 10 (8+2=10), then add the remaining 3 (10+3=13).
Q3. What is the biggest sum within 20?
10 + 10 = 20 is the biggest sum when both numbers are 10 or less.
Q4. What are doubles?
Doubles are when both addends are the same: 6+6=12, 7+7=14, 8+8=16.
Q5. How is this different from addition within 10?
In addition within 10, the sum is at most 10. In addition within 20, the sum can go up to 20. We need new strategies like making 10 for larger sums.
Q6. What is the easiest way to add to 10?
Adding any single digit to 10 is simple: just put that digit in the ones place. 10+3=13, 10+7=17.
