Examples of what pupils should know and be able to do
Understand that multiplying a positive number by a number between 0 and 1 makes it smaller and that dividing it by a number between 0 and 1 makes it larger. Use this to check calculations and to estimate the order of magnitude of an answer.
- Rounding question - Rtf (rich text format) document (44Kb)
- Operations question - Rtf (rich text format) document (76Kb)
Probing questions
Multiplying makes numbers bigger. When is this statement true and when is it false?
Division makes things smaller. When is this statement true and when is it false?
How would you justify that dividing by 
is the same as multiplying by 2?
What if pupils find this a barrier?
Explore using a calculator.
For example, start with 100 and then multiply or divide by a succession of numbers to get to a target of 3 say. The numbers used must be between 0 and 1.
Ordering activities can be helpful. Give pupils sets of cards with appropriate calculations on them. Ask pupils in pairs to order the calculations according to the size of the answer. See Teaching mental mathematics from level 5: number page 13.
Pupils may need to revisit step 6.
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