Monday, 1 August 2011

The answer

Last week I blogged a blog about a maths problem that had been set for primary school homework.  I asked you how you'd solve the problem.

Here's how I solved it.  I thought like a child, which is how I solve a lot of problems.

A reminder of the problem: How do you work out which two whole numbers between 50 and 70 which, when multiplied together produce 4095?

I thought about what times tables a child should be expected to know at the age of nine and how those tables might relate to the question.

I realised that the number 4095 ended in a five which would mean that one of the numbers I was looking for (between 50 and 70) would have to be divisible by five but, because 4095 ends in a five, it would also have to end in a five.

This meant that one of the multipliers was either 55 or 65.  From here the maximum number of calculations the pupil has to do is two.  I did some long division (actually I cheated and used my calculator because it's decades since I've done any long division) and discovered that the multipliers are 65 and 63.

Ta da!

But I am in awe of the far more impressive calculations that many of you proffered.  I am not worthy (despite still having the scientific calculator that I had at school).  You can all have a sticker.

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