Question 1199026
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Four years ago, a mother was 4 times as old as her son.
In 4 years time, the sum of their ages will be 56 years.
Find the age of the mother when the son was born 
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            Below is the mental solution.



<pre>
Since in 4 years the sum of their ages will be 56 years,
      it means that the sum of their ages now is 56 - 4 - 4 = 48.


Since now the sum of their ages is 48 years,
      it means that the sum of their ages four years ago was 48 - 4 - 4 = 40.


Since four years ago the sum of their ages was 40 and the mother was 4 times as old as her son,
      it implies that at that time the son was 8 years old and the mother was 32 years old
      (it is the only place, where minimal mental step is required,
       but for most people it is a quite affordable effort).


Since the difference of their ages was 32-8 = 24 at that time, it means that the mother is 24 years older than the son.


In other terms, it means that the mother was 24 years old when the son was born.    <U>ANSWER</U>
</pre>

Solved.


The total time to solve this problem in this way is about and around of 10 seconds.



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Regarding the post by @josgarithmetic, I recommend you to tape your eyes and plug your ears 


in order for do not see and do not hear that gibberish, which this person writes in his posts.



In more soft terms, simply ignore his writing, for safety of your mind.