Mathematics workshop
Useful calculation strategies
Count on, make ten and exchange ones for tens.
Theory
Count on
Start with the larger addend and take as many steps as the second addend shows. There is no need to count the first group from one again.
Use the shown strategy to find the result.
Start: 6. Steps to add: 3.
6 + 3 = 9
Make ten
Split the second addend: fill ten first, then add the rest. The number of counters stays the same.
Use the shown strategy to find the result.
Fill the empty cells in the first ten. Move counters from the second frame.
8 + 5 = 13
Exchange one ten
One ten can be exchanged for ten ones and bundled again. The notation changes, but the quantity stays the same.
Exchange one ten in 24. How many loose ones will there be?
Each long block is 10. Each square is 1.
24 = 2 × 10 + 4
Add by exchanging
Add tens to tens and ones to ones. If there are ten or more ones, bundle ten of them into a new ten. Thus 34 + 28 makes 5 tens and 12 ones, then 6 tens and 2 ones.
Use the shown strategy to find the result.
Combine the tens and the separate ones first.
34 + 28
Subtract by exchanging
If there are not enough ones to subtract, exchange one ten. Then remove the tens and ones of the second number. The unremoved blocks are the remainder.
Use the shown strategy to find the result.
Each long block is 10. Each square is 1.
42 − 17
Equal expressions
An equals sign says both sides have the same value. The answer can be inside the expression on the right.
Complete the right side so that both sides are equal.
Complete the right group to match the quantity on the left.
7 + 5 = 8 + 4
Two steps and brackets
Brackets show which operation to do first. Find the amount left inside them, then add it to the first quantity.
Blocks in two boxes: 12 and 6. Remove 2 from the second box. How many remain altogether?
12 + (6 − 2) = 16
12 + (6 − 2) = 16
Practice
Explore the example: perform and reverse the action, then compare diagram and equation.
Use the shown strategy to find the result.
Start: 6. Steps to add: 3.
6 + 3 = 9
Games
Find the unknown. A hint helps, and that completion is counted separately.
Use the shown strategy to find the result.
Start: 10. Steps to add: 5.
10 + 5 = ?
Choose a number to check it straight away. When typing, press Enter to finish.