Correct Answer - Option 1 : 21 yrs
Given:
Present age of Kalyani is 9 times her son’s age.
11 years hence, the ratio of the ages of Kalyani and her son = 12 : 5
Calculation:
Let the present age of son be x
⇒ Present age of Kalyani be 9x
⇒ (x + 11)/(9x + 11) = 5/12
⇒ 12(x + 11) = 5(9x + 11)
⇒ 12x + 132 = 45x + 55
⇒ 45x – 12x = 132 – 55
⇒ 33x = 77
⇒ x = 77/33
⇒ x = 7/3
Present age of Kalyani = 9 × (7/3) years
⇒ 21 years
∴ Present age of Kalyani is 21 years