Q : The ratio of ages of father and son is 3:1. Four years earlier, the ratio was 4:1. What are the present ages of both father and son?

Solution:

Father : son

Present age= x:y

P years before= a:b

Then son’s age= [yP(a-b)/(difference of cross product)]

Father’s age= [xP(a-b)/(difference of cross product)]

Note: difference of cross product = xb-ay or ay-xb

Remember to subtract smaller from larger so that difference of cross product always comes positive.

Solve this question. The answer will be

Son’s age = {1*4(4-1)}/{(4*1)-(3*1)} = 12 years

Father’s age = {3*4(4-1)}/{(4*1)-(3*1)} = 36 years

Father : son

Present age= x:y

P years before= a:b

Then son’s age= [yP(a-b)/(difference of cross product)]

Father’s age= [xP(a-b)/(difference of cross product)]

Note: difference of cross product = xb-ay or ay-xb

Remember to subtract smaller from larger so that difference of cross product always comes positive.

Solve this question. The answer will be

Son’s age = {1*4(4-1)}/{(4*1)-(3*1)} = 12 years

Father’s age = {3*4(4-1)}/{(4*1)-(3*1)} = 36 years

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