Question : Directions: The ratio of present ages of A and B is 5 : 7. If the age of B after 10 years is 31 years, then what is the present age (in years) of A?
Option 1: 10
Option 2: 15
Option 3: 25
Option 4: 35
Correct Answer: 15
Solution :
Given:
The ratio of present ages of A and B is 5 : 7
⇒A's present age = 5 × Y
⇒B's present age = 7 × Y
The age of B after 10 years is 31 years,
⇒(7 × Y) + 10 = 31
⇒(7 × Y) = 31 – 10 = 21
⇒Y = 21 ÷ 7 = 3
⇒Y = 3
Therefore, the present age of A is 5 × Y = 5 × 3 = 15 years. Hence, the second option is correct.
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