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We can multiply two-digit numbers by two-digit numbers using efficient written methods
Year 6 Unit 10a
What we are learning:
Efficient written methods are short and quick to complete, but are backed up by a strong understanding of what is happening in a calculation.
This is why we start with expanded methods first before shortening them to efficient methods later.
When we multiply a two digit number by another to digit number, e.g. 34×42 we set it out like this and to begin we multiply 34 by the two units.
The shading in this example shows which part of the calculation we are doing:
Next we multiply 34 by 40 (because the 4 represents 4 tens or 40). To do this we insert a zero in the units column and them we multiply 34×4 (because 10×4=40) so if we insert a zero we are multiplying by 10 first and then by 4.
Finally we can add the two rows together to find the answer.
So 34×42 = 1428
Activities you can do at home:
Use the digits 6, 4, 7 and 5 to create two pairs of two-digit numbers and then find the product of these numbers. E.g. 75 x 64, 54 x 76. What is the largest product you can make?
If your child:
Makes calculation errors when multiplying or adding
Slow down their calculation and ask them to talk it through out loud as they do it – this often helps them identify their own errors and they self correct them as they realise. If they don’t see their error, ask them Are you sure
about that part? This will prompt them to look at it more carefully again.