Question

A sum of money doubles itself in 5 years in how many years will it become four fold

Answer 1

15 years is ur answer. Hope u got it

Answer 2

Concept:

The principal is the money invested for a period of time at a certain rate of interest and the amount is the money received after that period of time with interest.

Given:

The amount becomes double of principal in 5 years.

Find:

Time taken by the amount to become four times of principal.

Solution:

Take the Principal as P, rate as r, time as T, interest as I, and amount as A.

When Principal is P and time is 5, the amount is 2P.

A = 2P

A = P + P

A = P + I

Interest is equal to principal.

Find the rate.

I = $\frac{PrT}{100}$

P = $\frac{5Pr}{100}$

P = $\frac{Pr}{20}$

r = 20%

When Principal is P and Amount is 4P.

A = 4P

A = P + 3P

I = 3P

I = $\frac{PrT}{100}$

3P = $\frac{20PT}{100}$

3P = $\frac{PT}{5}$

15P = PT

T = 15

Hence, the time taken for a sum of money to become four times is 15 years.

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