Question

A sum of money triples itself in four years. Find the time required for it to become 5 times.

• A. 6 years
• B. 8 years
• C. 10 years
• D. 12 years

Answer 1

The correct option is B 8 years

Given, time = 4 years.
Let the sum invested be ₹ 100.
So, the Amount received after 4 years = ₹ 300.

We know that,
Principal + Interest = Amount.
Hence, Interest = Amount - Principal = ₹ (300-100) = ₹ 200.

The Simple Interest earned on a sum of ₹ P for a period of T years at the rate of R% p.a S.I is given by $\frac{P\times R\times T}{100}$.

So, ₹ 200 = $\frac{100\times R\times 4}{100}$
Hence, R = 50%.

Now, for the amount to become 5 times i.e ₹ 500,
The interest needed to be earned is ₹(500-100) = ₹ 400.
So, ₹ 400 = $\frac{100\times 50\times T}{100}$
Hence, the time taken = T = 8 years.