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How old am I?

How old am I?

If you multiply the two digits corresponding to my age, you get half of the years I am.

How old am I?

Solution

I `m 36 years old. 3 × 6 = 18 which is half of 36. From the statement we can deduce the following equation:
X × 10 + Y = 2 × X × Y

If we clear for example X, where we get that Y = 2XY - 10X = X (2Y-10) from where we deduce that X = Y / (2Y-10)
If we look for all the whole solutions of X and Y where each X and every Y be composed of a single digit we find that there is only one: X = 3 and Y = 6