Question 75

A sum is invested at simple interest. If the rate of interest is 20% per annum, then in how much time will it become double of itself?

Solution

$$2P = P + \frac{P\times\ R\times\ T}{100}$$

Where P = principal amount

R = rate of interest

T = time

$$2P = P + \frac{P\times\ 20\times\ T}{100}$$

$$2P-P\ =\ \frac{P\times\ 20\times\ T}{100}$$

$$P\ =\ \frac{P\times\ 20\times\ T}{100}$$

$$1\ =\ \frac{\ 20\times\ T}{100}$$

$$1\ =\ \frac{\ T}{5}$$

T = 5 years

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