Grade 2 · Unit 1: Number and place value

Subtracting in your head

Count back, or count on to find the difference.

Fish for sale at a market. When some are sold, fewer are left.

How many are left?

A fish seller has 40 fish and sells 20. How many are left? We subtract. 40 − 20 = 20.

Counting back in tens

To take away tens, count back in tens. 76 − 30: 66, 56, 46. The ones digit stays the same.

Counting on to find the difference

When numbers are close, count on. From 47 to 50 is 3. From 50 to 53 is 3 more. The difference is 6.

Use what you know

If you know 8 − 3 = 5, you know 80 − 30 = 50. You also know 18 − 3 = 15. Look for patterns to subtract quickly.

What I learnt