Word Problems: Add & Subtract Within 20 — Answer Key
Part A: Show Your Work
Read each problem carefully. Use the box to show your work.
1. Noah had some toy cars. He got 6 more and now has 14. How many toy cars did Noah start with?
Answer: 8 toy cars
Work backward by subtracting: 14 - 6 = 8 cars at the start.
2. There were 16 fish in a pond. Some fish swam away and now there are 9. How many fish swam away?
Answer: 7 fish
Subtract to find the missing part: 16 - 9 = 7 fish swam away.
Part B: Solve Without a Work Box
Read each problem and write the answer on the line.
1. Mia has 11 buttons. She needs 20 buttons for her art project. How many more buttons does she need?
Answer: 9 buttons
Subtract to find the difference: 20 - 11 = 9 more buttons needed.
2. A shelf has 8 big books and 7 small books. If 5 books are taken off, how many books are left?
Answer: 10 books
First add: 8 + 7 = 15 books. Then subtract: 15 - 5 = 10 books left.
Part C: Think About It
Write the missing number on each line.
1. 7 + 8 = 15
Think about what number plus 8 makes 15: 15 - 8 = 7, so 7 + 8 = 15.
2. 20 - 7 = 13
Think about what number taken from 20 leaves 13: 20 - 13 = 7.
3. If 9 + 6 = 15, then 15 - 9 = 6.
Addition and subtraction are related: since 9 + 6 = 15, taking 9 away from 15 gives back 6.
4. Dan had 18 cards. He lost some and now has 11. He lost 7 cards.
Subtract to find the lost cards: 18 - 11 = 7 cards lost.