The average age of Raj and his father is 45 years. If the ages of the father and the grandfather of Raj are respectively two and three times that of Raj, then the age of Raj's grandfather is

Correct option is B

Given:
Average age of Raj and his father = 45 years

=> Sum of their ages = 45 × 2 = 90 years

Father's age = 2 × Raj's age

Grandfather's age = 3 × Raj's age

Formula Used:
Average = (Sum of ages) ÷ Number of people

Father's age = 2 × Raj's age

Grandfather's age = 3 × Raj's age

Solution:
Let Raj's age be x.
Then Father's age = 2x

Now,
x + 2x = 90
=> 3x = 90
=> x = 30 (Raj's age)

Now,
Grandfather’s age = 3 × x = 3 × 30 = 90 years

Ans. (b) 90 years