63.A father is four times as old as his son today. After 20 years, he would be just twice as old. At the time of birth of his son, how much old must the father be?
[A] 31
[B] 30
[C] 37
[D] 38
Answer : B
Explanation :
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Let the ages of son and father today by 'x' and '4x' years respectively.
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4x + 20 = 2 (x + 20) ---> As per information
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x = 10 years ==> 4x = 40 years.
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At the time of birth of his son, father must be 40 - 10 = 30 old
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