Four years ago, the age of the mother was 13 times the age of her daughter. Two years hence, the mother's age will be 4 times the daughter's age. After how many years will the mother's age be 3 times that of her daughter?
Four years ago, the age of the mother was 13 times the age of her daughter. Two years hence, the mother's age will be 4 times the daughter's age. After how many years will the mother's age be 3 times that of her daughter? Correct Answer 6
Given:
Four years ago, the age of the mother was 13 times the age of her daughter.
Two years hence, the mother's age will be 4 times the daughter's age.
Calculation:
Let the present age of the daughter be Q years.
Four years ago, the age of the daughter = (Q - 4) years
Four years ago, the age of the mother = 13 × (Q - 4)
⇒ (13Q - 52) years
Two years hence,
Age of the daughter = (Q - 4) + 4 + 2 = (Q + 2) years
Age of the mother = (13Q - 52) + 4 + 2 = (13Q - 46) years
According to the question,
(Q + 2) × 4 = (13Q - 46)
⇒ 4Q + 8 = 13Q - 46
⇒ 13Q - 4Q = 46 + 8
⇒ 9Q = 54
⇒ Q = 54/9
⇒ Q = 6
Now, the present age of the mother = (13Q - 52) + 4
⇒ 13Q - 48
⇒ 13 × 6 - 48
⇒ 30
Let after M years the age of the mother will be three times of her daughter.
According to the question,
(6 + M) × 3 = (30 + M)
⇒ 18 + 3M = 30 + M
⇒ 2M = 30 - 18
⇒ M = 12/2
⇒ M = 6
∴ After 6 years the mother's age will be 3 times that of her daughter.