P.1 Complete the addition sentences - sums up to 20
Understanding Addition up to 20
When we add numbers, we put groups together to find the total, called the sum. In first grade, we practice adding numbers where the total is 20 or less.
- 9 + 6 = 15 means nine and six together make fifteen.
- 8 + 7 = 15 shows eight added to seven equals fifteen.
- 10 + 5 = 15 means ten and five together make fifteen.
Adding numbers up to 20 builds on what you know about sums up to 10. Use what you already know to help solve larger problems.
Making a Teen Number (10 and Some More)
A teen number can be thought of as 10 and some more. This helps us understand numbers from 11 through 20.
- 10 + 4 = 14 means ten and four make fourteen.
- 10 + 7 = 17 shows seventeen is ten and seven more.
- 10 + 9 = 19 means nineteen is ten plus nine.
Think of teen numbers as “ten and ones.” For example, 16 is ten and six ones.
Finding the Missing Number
Sometimes, we solve addition problems by finding the missing number. This helps us understand number pairs that make a total up to 20.
- 12 + ? = 20. Since 12 needs 8 more to make 20, the missing number is 8.
- ? + 9 = 15. Think: “What plus 9 equals 15?” The answer is 6.
- 7 + ? = 18. The missing number is 11.
Remember number pairs to 20: 11+9, 12+8, 13+7, 14+6, 15+5, and so on. These facts will help you solve problems quickly.
Using Objects and Drawings
We can use real objects, counters, or drawings to help us see how numbers work together and make larger sums.
- Put 8 red cubes and 7 blue cubes together. Count them all: 8 + 7 = 15.
- Draw 12 stars, then add 6 more. Count them: 12 + 6 = 18.
Use things around you like coins, pencils, or blocks. Drawing pictures also helps make addition easier to understand.
Adding on a Number Line
A number line helps us add by starting at one number and hopping forward to add the other number until we reach the total.
- Start at 11 on the number line. Move 5 steps forward. You land on 16. So, 11 + 5 = 16.
- Start at 7. Move 9 steps forward. You land on 16. So, 7 + 9 = 16.
Always move to the right when adding. The farther you go, the bigger the number becomes.
Addition in Everyday Life
We use addition every day when we put groups together or find totals in real situations.
- You have 8 toy cars and your friend gives you 6 more. Now you have 8 + 6 = 14 toy cars.
- There are 9 birds on a fence. 8 more land. Now there are 9 + 8 = 17 birds.
- You eat 7 grapes in the morning and 5 in the afternoon. That’s 7 + 5 = 12 grapes in all.
Look around your home or classroom. Group objects and add them to see how numbers combine to make a total up to 20.