-
A sum borrowed under compound interest doubles itself in 10 years. When will it become fourfold of itself at the same rate of interest ?
-
- 15 years
- 20 years
- 24 years
- 40 years
Correct Option: B
Let the sum be P which becomes 2P in 10 years. Hence, 4P in 20 years .
We can find required answer with the help of given formula :
Unitary Method can also be used.
Here, m = 2, t = 10
Time taken to become 4 times = 22 times
∴ Time taken to become 4 times = t × n = 10 × 2 = 20 years
