Question

A bank offers, continuously increasing principal at the rate of 8% per year. Rohit thought to  invest 16000Rs then how much long will it take for him to double the value invested by him?

Answer 1

R = 8%, P = Rs. 16000, A = Rs. 32000

Let after n years Rohit will get money to double the value invested by him.

\(\because A=P(1+\frac R{100})^n\) 

⇒ 32000 = 16000(1 + \(\frac{8}{100}\))ⁿ

⇒ (1 + \(\frac{2}{25}\))ⁿ = \(\frac{32000}{16000}=2\)

⇒ \((\frac{27}{25})^n=2\)

⇒ n log \(\frac{27}{25}\) = log 2

⇒ n = \(\frac{log2}{log1.08}\) = \(\frac{0.3010}{0.33423}\approx9\)

Almost, n = 9 years Rohit will double money as he invested.