Question

In a bank , principal increases continuously at the rate of 5% per year . In how many years Rs 1000 double itself

Answer 1

The problem appears to be that of compound interest.
A = P (1 + r/100)^n
A = Amount of n years,  P = principal,  r= rate of interest
2P= P (1 + 5/100)^n
2 = 1.05^n
Log 2 = n * Log 1.05
n = 14.2 years 

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For the case of simple interest:

interest = P * r* n/100 
For doubling principal, interest = principal
So r*n = 100  =>  n = 100/5 = 20 years

Answer 2

Heres the answer gopal
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