Tejas gets double the amount in 11 years when invested at compound interest, compounded annually. In how many years will the amount become four times itself?

Correct option is D

Given:

A certain sum doubles in 11 years under compound interest

We are to find the time it takes for the sum to become four times itself

Concept Used:

From compound interest principles:

If an amount becomes t times of itself in m years,

then it becomes tⁿ times of itself in m × n years.

This is based on exponential growth in compound interest:

If A = P × t in m years, then A = P × tⁿ in m × n years

Solution:

Here,

t = 2 (doubling)

m = 11 years

To become 4 times => 2², so n = 2

Now apply the formula:

Time = 11 × 2 = 22 years