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Count on from the bigger
Joyful Mathematics: Chapter 6
GoalAdd by counting on from the bigger number.
New words
count on · say the next numbers after the big onebigger · the larger numberfingers · help us keep track
Explanation
Start with the bigger number. Then count on. 14 + 3: say 14 in your head. Then count on 3 fingers: 15, 16, 17. So 14 + 3 = 17. Do not count from 1. You can start with the bigger number even when it comes second.
Worked examples
11 + 5 = 16. Say 11. Then count on 5: 12, 13, 14, 15, 16.
3 + 15: start with the bigger number, 15. Count on 3: 16, 17, 18. So 3 + 15 = 18.
17 + 2 = 19. Say 17. Then count on 2: 18, 19.
Class activity
Count on from 15. The grown-up puts 15 stones in a bowl and says "There are 15." The child adds 3 more stones, one at a time, and says 16, 17, 18 without starting again from 1. Try other starting numbers.
Practice
1
Start at 13. Count on 6. What number do you reach?
19.
2
What is 15 + 5?
20.
3
What is 12 + 3?
15.
4
Start at 10. Count on 8. What number do you reach?
18.
5
Start at 18. Count on 2.
20.