If 5 times a son’s age is added to his father’s age, the sum is 79 years. If 2.5 times the father’s age is added to the son’s age, the sum is 94 years. What is the father’s age (in years)?

Correct option is D

Given:

Let father's age = F

Let son's age = S

5S + F = 79 .......(1)

S + 2.5F = 94 .......(2)

Solution:

from first equation:

F = 79 - 5S

Substitute in second equation

S + 2.5(79 - 5S) = 94

S + 197.5 - 12.5S = 94

-11.5S = 94 - 197.5

-11.5S = -103.5

S = 9

Now,  father’s age

F = 79 - 5(9) = 79 - 45 = 34 years