Decide on the most efficient subtraction strategy, including column subtraction | Maths

Starter quiz

Where is regrouping needed in this column subtraction?
- Regrouping is needed in the ones.
- Regrouping is needed in the tens.
- Regrouping is needed in the ones and tens.
- Regrouping is not needed. ✓
Where is regrouping needed in this column subtraction?
- Regrouping is needed in the ones.
- Regrouping is needed in the tens.
- Regrouping is needed in the ones and tens. ✓
- Regrouping is not needed.
Complete the column subtraction. What is the difference between the two numbers?
- '172' ✓
Calculate the difference using column subtraction.
- '433' ✓
Calculate the difference using column subtraction.
- '193' ✓
Calculate the difference using column subtraction.
- '325' ✓

Exit quiz

Which calculations would it be most efficient to answer using a mental strategy?
- 368 − 99 = ✓
- 671 − 356 =
- 292 − 288 = ✓
- 255 − 168 =
Which calculations would it be most efficient to answer using column subtraction?
- 476 − 376 =
- 444 − 278 = ✓
- 331 − 165 = ✓
- 557 − 555 =
What is the most efficient way to calculate 368 − 99 =?
- Start at 99 and count on to 368
- Use column subtraction
- Subtract 100 then add 1 ✓
- Subtract 100 then subtract 1
What is the difference between 292 and 288?
- '4' ✓
Evie and baby Elias have a total length of 605 cm. If baby Elias has a length of 205 cm, how long is Evie? Evie is ______ cm long.
- '400' ✓
Elodie and baby Emily have a total length of 611 cm. If Elodie has a length of 437 cm, how long is baby Emily? Emily is ______ cm long.
- '174' ✓

Worksheet

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Presentation

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Lesson Details

Key learning points

Look carefully at the numbers in a calculation.
Column subtraction might be the most efficient method to use if regrouping is needed.
Use a mental strategy where it would be more efficient.

Common misconception

When using adjustment (e.g. 456 − 199), pupils may forget whether they have to subtract or add 1 after they have subtracted 200

Ask pupils if they subtract 200 then subtract 1 more, how much have they subtracted altogether? They should see that they have subtracted 201, not 199 A number line representation will support pupil's understanding with this.

Keywords

Efficient - Being efficient means finding a way to solve a problem quickly whilst also maintaining accuracy.
Mental strategy - A mental strategy is a method chosen to find something out which can be done in your head or with some jottings.
Regroup - The process of unitising and exchanging between place values is known as regrouping.