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Puzzle ZNTH 



?

My current age is the age of my favourite book (which is 14 years old) plus one third of my age.

How old will I be when my favourite book is twice its current age?

Puzzle Copyright © Kevin Stone

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Answer
I will be 35 in 14 years.

Reasoning
I am currently 21.

If X is my current age, then:
  X = 14 + X
           —
           3
so

  2X = 14
  ——
   3

and

  2X = 42

So

  X = 21

I am currently 21 and my favourite book is currently 14 years old, when it is 28 years old (double its age) I will be 35.

 

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