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It's problem solving Friday - you need to log onto Mathletics and I am Thinking of a Number!


This one is all about what in maths we call inversion, also called a backwards sum.


So if I said to you, I am thinking of a number, add seven and get twenty four. What's that number? 

First we need to 'translate' those words into some maths.

? + 7 = 24


Something add 7 is 24.

Next, let's get our inversion on. Turn it into a backwards sum. If we added 7 to get 24, if we take 7 from 24 we'll get that number.


24 - 7 = ?


So our number is...17


One more! I'm thinking of a number, double it and get twenty. What's that in maths...

? x 2 = 20


Work backwards - the inverse of x is ÷.


20 ÷ 2 = ?


So our mystery number is...10!


Good luck, get those thinking caps on and don't forget about that little grey 'i' on Mathletics if you get stuck.