12 year old Manick is three times as old as his brother Rahul. How old will Manick be when he is twice as old as Rahul ?
Answer: B
Manick's present age = 12 years, Rahul's present age = 4 years.
Let Manick be twice as old as Rahul after x years from now.
Then, 12 + x = 2 (4 + x)
\(\Rightarrow 12 + x = 8 + 2x\)
\(\Rightarrow x = 4.\)
Hence, Manick's required age = 12 + x = 16 years