Take Away Whole Tens
Find a difference by removing groups of ten.
Supplied materials
- Paper and pencil, or a trusted adult to record spoken reasoning.
- Supplied starting picture: six ten-boxes and no loose ones.
Learn the idea
Subtraction can remove whole groups. A box representing ten dots has a value of ten, so crossing out two ten-boxes removes twenty dots. Count the boxes still present, then say their value in tens.
We will subtract multiples of ten. There are no loose ones to change. You can check subtraction by putting the removed groups back: the remaining amount plus the removed amount must equal the starting amount.
- Draw six ten-boxes for 60.
- Cross out two boxes to show subtracting 20; count four boxes remaining.
- Check 40 + 20 = 60, then solve 80 − 30 with eight ten-boxes.
See the method in action
60 − 20 = 40 because six tens minus two tens leaves four tens. The check is 40 + 20 = 60.
Check your reasoning
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See the answer and explanation
50
Eight tens minus three tens leaves five tens: 80 − 30 = 50. The answer is fifty, not five single dots.
Take it further
Take away five tens from 80 instead. Three tens remain, so 80 − 50 = 30. Check by adding 30 + 50 to rebuild 80.
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