Today, the age of a father is thrice the age of his son. After 5 years the age of father will be 2.5 times the age of his son. What is the age of son today?
20 years
15 years
1 years
22 years
Explanation:
Let the age of son = S years and the age of father = F years.
According to the question,
=> F = 3 $\times$ S.
=> F = 3S.
After 5 years,
=> (F+5) = 2.5 $\times$ (S+5).
=> 3S + 5 = 2.5S + 12.5 [put F=3S]
=> 0.5S = 7.5
=> S = 15
Hence, the age of son = 15 years.