Starter quiz
- How should you partition 5 to calculate 98 + 5?
- add 2 then add 3 ✓
- add 3 then add 2
- add 4 then add 1
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- Which calculations cross a 100s boundary?
- 190 − 30
- 210 − 30 ✓
- 220 + 30
- 190 + 30 ✓
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- What is 230 + 30?
- '260' ✓
- 270 − 40 = ______
- '230' ✓
Which calculation is shown by the number line representation?- 397 + 3 = 403
- 397 + 5 = 403
- 396 + 6 = 403
- 397 + 6 = 403 ✓
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Use the number line to find the missing number. 510 − ___ = 460- 10
- 20
- 40
- 50 ✓
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Exit quiz
- How should you partition 60 to calculate 160 + 60?
- add 20 then add 40
- add 30 then add 30
- add 40 then add 20 ✓
-
- How should you partition 60 to calculate 210 − 60?
- subtract 10 then subtract 50 ✓
- subtract 20 then subtract 40
- subtract 30 then subtract 30
-
- 245 + 20 = ______
- '265' ✓
- 320 − 40 = ______
- '280' ✓
Colin the cat is 410 cm high in a tree. He climbs down 50 cm. How high is he now?- 350 cm
- 360 cm ✓
- 460 cm
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- Katya is in a tree. She climbs down 30 cm. She is now 288 cm high. How high was she when she started? ______ cm
- '318' ✓
Worksheet
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Presentation
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Video
Lesson Details
Key learning points
- Number lines can record the steps in our thinking when we are partitioning to add and subtract.
- The 1s digit does not change when you add or subtract a multiple of ten.
- Number facts to 10 help when crossing the 10s and 100s boundaries.
Common misconception
Pupils may struggle to partition 10s numbers to help them bridge a 100s boundary.
Encourage pupils to calculate the number of tens needed to add or subtract to the 100s number, then add or subtract the remainder.
Keywords
Bridge - Bridging is a strategy which uses addition or subtraction to cross a number boundary.
Partition - Partition means splitting an object or value down into smaller parts.
100s boundary - The 100s boundary is the point at which the numbers change into 100s numbers, or from one set of hundreds to another.
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