Question

A principal amount of ₹4000 has been increased to ₹5000 in 8 years. In what time will an amount of ₹1600 increase to ₹2400 at the same rate of interest?

Answer 1

Principal (P) = ₹ 4000 ; Amount = ₹ 5000 , hence I = ₹ 5000 - 4000 = ₹ 1000
Let the Rate be (R)
Time (n)= 8 years

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

1000 = $\frac{4000\times 8\times R}{100}$

R = $\frac{25}{8}$ %

In the second case Given P = 1600 and Amount = ₹ 2400 , Hence I = ₹ 2400 - 1600 = ₹ 800

Let the time be n and rate of interest = $\frac{25}{8}$ %

800 = $\frac{1600\times 25\times n}{100\times 8}$

n = $\frac{800\times 8\times 100}{1600\times 25}$

n = 16 years