Question

A is elder to B by 2 years. A's father F is twice as old as A and B is twice as Old as his sister S. If the ages of the father and sister differ by 40 years, find the age of A.

Answer 1

A = B + 2
F = 2A
B = 2S. Substituting for B from 1st equation,
A - 2 = 2S. S = (A - 2)/2

F - S = 40
2A - (A - 2)/2 = 40
3A/2 = 39
A = 26

Answer 2

According to question we have:
A - B = 2 ........eq(1)
and F - S = 40 ........eq(2)
We also have
F = 2A and B = 2S
Now putting the above value in eq(2) we have
2A - (B/2) =40
=>4A - B= 80 .......eq(3)
Now subtract eq(3) by eq(1) whe have
3A = 78
Therefore A = 26 years