Q. In 10 years A will be twice as old as B was 10 years ago. If A is now 9 years older than B, what is the present age of B?
✅ Correct Answer: (B)
39 years
Explanation: Let the present age of B and A be x and ( x + 9 ) years; then,
Age of B and A after 10 years will be x + 10 and x + 9 + 10;
According to question,
In 10 years A will be twice as old as B was 10 years ago
2(x - 10) = x + 9 + 10
2x - 20 = x + 19
⇒ 2x - x = 19 + 20
∴ x = 39 years
Explanation by: Harikesh
Let the present age of B and A be x and ( x + 9 ) years; then,
Age of B and A after 10 years will be x + 10 and x + 9 + 10;
According to question,
In 10 years A will be twice as old as B was 10 years ago
2(x - 10) = x + 9 + 10
2x - 20 = x + 19
⇒ 2x - x = 19 + 20
∴ x = 39 years
Age of B and A after 10 years will be x + 10 and x + 9 + 10;
According to question,
In 10 years A will be twice as old as B was 10 years ago
2(x - 10) = x + 9 + 10
2x - 20 = x + 19
⇒ 2x - x = 19 + 20
∴ x = 39 years