If a sum of money doubles itself in 10 years on compound interest, then in how many years will it become 16 times of itself at the same rate of interest?

Correct option is C

​Given:

A sum doubles in 10 years.

Formula Used:

Compound interest doubles the amount at constant intervals,

so the time to multiply by 2ⁿ is $$n \times \text{doubling time}$$​​

Solution:

To become $$16 \times itself$$​:

​$$16 = 2^4 \quad \text{(4 doublings)}$$ 

So, time required to became 16 times,

Time = $$4\times 10 = 40 \, \text{years}$$​​