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Solution: multiplying by 25

Solution: multiplying by 25
Let’s use the same strategy to work out the answer to the question 14 times 25. I’m going to use again the fact that there are four 25s into 100. So instead of multiplying 14 by 25 I’m going to do 14 times 100. So if this is 14 times a 100, which is 1400, I’m going to split that into four equal parts. Each of which will be the equivalent of 14 times 25. So I’m going to divide 1400 by 4. Now, this is not a division that perhaps you can do in a straightforward way in your head.
And one easy way, one easy strategy to apply, in order to divide any number by 4 is to divide the number by 2, and then divide that answer by 2 again. This is what I’m going to do. I’m going to do 1400 divided by 2, which is 700, and then I’m going to divide that by 2 again. And this is 350. And it gives me the answer to the question 14x25=350.

This is a solution video for the previous task where you were asked to mentally multiply by 25.

The task is to calculate 14 times 25.

Hint 1: When we multiply by 100 it makes the number 100 times bigger.

Hint 2: When we then divide by 4, so a quarter of 100, we have done the equivalence of multiplying by 25.

Note: These tasks come from ‘Max Maths Primary – A Singapore Approach’.

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World Class Maths: Asian Teaching Practice

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