SOLUTION: In what time will rupees 1000 becomes Rs. 1331 at 10% rate p.a compound interest.

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Question 1087136: In what time will rupees 1000 becomes Rs. 1331 at 10% rate p.a compound interest.
Answer by Theo(13342) About Me  (Show Source):
You can put this solution on YOUR website!
f = p * (1 + r) ^ n

f is the future value
p is the present value
r is the interest rate per time period
n is the number of time periods.

in your problem:

f = 1331
p = 1000
r = .1 per year
n = number of years

the formula becomes:

1331 = 1000 * (1 + .1) ^ n

divide both sides of the equation by 1000 and simplify to get:

1.331 = 1.1 ^ n

take the log of both sides of the equation to get:

log(1.331) = log(1.1 ^ n)

simplify to get log(1.331) = n * log(1.1)

solve for n to get n = log(1.331) / log(1.1) = 3

1000 rupees will become 1331 rupees in 3 years at an interest rate of 10% compounded annually.

in general, log(b^n) = n*log(b)

that's one of the basic properties of logarithms.