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O.1 Addition using number lines - sums up to 20

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Adding on a Number Line

A number line is a tool that helps us see how numbers grow. When we add, we start at one number and move forward to find the sum.

Examples:
  • Start at 6. Move 3 steps forward. You land on 9. So, 6 + 3 = 9.
  • Start at 8. Move 5 steps forward. You land on 13. So, 8 + 5 = 13.
  • Start at 10. Move 7 steps forward. You land on 17. So, 10 + 7 = 17.
Helpful Hint

Always move to the right when adding on a number line because the total gets larger.

Counting On with a Number Line

Instead of starting at zero, we can begin at the first number and count on the second number of steps.

Examples:
  • For 7 + 2, start at 7. Count on 2 more: 8, 9. So, 7 + 2 = 9.
  • For 12 + 4, start at 12. Count on 4 more: 13, 14, 15, 16. So, 12 + 4 = 16.
Helpful Hint

Counting on is faster than starting from zero every time. Use the bigger number first.

Making Jumps of Ten

We can use the number line to make quick jumps of ten, then smaller jumps to finish the addition. This helps with larger numbers up to 20.

Examples:
  • To solve 9 + 7: start at 9, jump 1 to get to 10, then jump 6 more to land on 16. So, 9 + 7 = 16.
  • To solve 14 + 5: start at 14, jump 5 steps to land on 19. So, 14 + 5 = 19.
Helpful Hint

Breaking numbers apart helps make addition easier. Think about how to reach the next ten before adding the rest.

Real-Life Addition on a Number Line

We can use number lines to solve everyday problems, like counting items or keeping track of scores.

Real-Life Examples:
  • You have 8 toy cars. You get 6 more. Start at 8, move 6 steps forward. You land on 14. So, 8 + 6 = 14.
  • You read 10 pages yesterday and 7 more today. Start at 10, move 7 steps. You land on 17. So, 10 + 7 = 17.
Try This

Draw your own number line on paper. Use it to solve story problems about your toys, books, or snacks.