Decide on the most efficient subtraction strategy, including column subtraction
I can make efficient use of subtraction strategies, including column subtraction.
- Year 4
Decide on the most efficient subtraction strategy, including column subtraction
I can make efficient use of subtraction strategies, including column subtraction.
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.
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.
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.
Licence
Lesson video
Loading...
Prior knowledge starter quiz
6 Questions
Q1.Where is regrouping needed in this column subtraction?
Q2.Where is regrouping needed in this column subtraction?
Q3.Complete the column subtraction. What is the difference between the two numbers?
Q4.Calculate the difference using column subtraction.
Q5.Calculate the difference using column subtraction.
Q6.Calculate the difference using column subtraction.
Assessment exit quiz
6 Questions
Q1.Which calculations would it be most efficient to answer using a mental strategy?
Q2.Which calculations would it be most efficient to answer using column subtraction?
Q3.What is the most efficient way to calculate 368 − 99 =?
Q4.What is the difference between 292 and 288?
Q5.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.
Q6.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.
