Cover Up
The setup
This activity combines the approaches of ‘What’s Missing?’ from Stage 2 and ‘Shape Sums’ of Stage 3. Take a collection of small objects, count them, and spread them out on a surface. Use pieces of paper, cloth, or bowls to cover over one or more groups of the objects. Use the same color paper when covering groups of the same size.
The challenge
Find out how many objects are in each covered group.
Four Steps
- Count the number you can see and compare to the total.
- Find one way to solve it.
- Find other ways to solve it.
- Verify your answer(s).
Example
As pictured above, suppose you have 18 items and you cover 14 of them with two red pieces of paper. Your child sees the number 18 and that there are 4 uncovered items. They can subtract 18 – 4 and know that 14 pieces are covered. Because the same color is used, the covered items must be equal, so each must be 7, which is half of 14.
Here is where the best, and most important, ‘step’ starts. What other ways are there of discovering that each covered group has 7 items? Your child could count by 2’s and see that there are seven 2’s as they skip count from 4 to 18. They could break 18 into halves of 9 each and break the 4 into halves of 2 each – then each group of 9 consists of a covered group plus 2 more, so the covered groups are 7 each.
Keep exploring and thinking of ways to use all the interesting math relationships!