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Counting up and back
Discover Mathematics: Chapter 3
GoalCount from 0 to 15 and back again, and find a missing number in a counting row.
New words
forward · counting up: 1, 2, 3backward · counting down: 3, 2, 1missing · not there, hidden
Explanation
We can count forward: 0, 1, 2, 3, all the way to 15. Each number is one more than the one before. We can also count backward: 15, 14, 13, down to 0. Each number is one less than the one before. Sometimes a number is hidden in a counting row. Look at the numbers on both sides. In 11, 12, ?, 14, the hidden number comes after 12 and before 14, so it is 13.
Worked examples
Marwan counts the sailing boats on the Nile forward: 1, 2, 3, up to 12. There are 12 boats.
A rocket count-down goes backward: 5, 4, 3, 2, 1, 0. Blast off!
Look at 11, 12, ?, 14, 15. The missing number is 13, because it comes after 12 and before 14.
Class activity
Stair count. Count the steps of a staircase or the tiles on a path, going up to 15, then come back down counting backward to 0. Next time, the grown-up covers one number with a hand and the child says the missing number.
Practice
1
How many planes are there?
13
2
How many trees are there?
15
3
Count backward from 8 to 0.
8, 7, 6, 5, 4, 3, 2, 1, 0
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Find the missing number: 7, 8, ?, 10, 11.
9
5
Find the missing number: 15, 14, ?, 12.
13