Mathematricks: The solution‏

By Morwenna Evans Monday, March 31, 2014

Last week we gave you a tricky brain teaser to get your teeth into. Today we're revealing the answer and showing you the tricks behind the maths.

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If we assume that these are all equations and use X to represent an unknown number …

8 x X = 56
7 x X = 42
6 x X = 30
5 x X = 20

3 x X = ?

… it becomes clear that X is always the first number - 1.

8 x X = 56 -- so -- 8 x 7 = 56
7 x X = 42 -- so -- 7 x 6 = 42
6 x X = 30 -- so -- 6 x 5 = 30
5 x X = 20 -- so -- 5 x 4 = 20

4 x X = ? was missing from the original list

If we follow the previous pattern …

4 x X = 12 so … 4 x 3 = 12

3 x X = ? so … 3 x 2 = 6

The answer is 3 = 6