Question 887032: A certain sum amount to Rs 14400 at 4% simple interest in a period of time in which Rs 9000 amounts to Rs 12150 at 7%. find the sum. Answer by Theo(13342) (Show Source):
You can put this solution on YOUR website! the simple interest formula is as follows:
f = p + i * n * p which can be simplified to:
f = p * (1 + i * n)
f is the future value
p is the present value or principal
i is the interest rate per time period
n is the number of time periods.
you are given that 9000 grows at 7% per year for n years and results in 12150.
substitute in the equation of f = p * (1 + i * n) to get:
12150 = 9000 * (1 + .07 * n)
divide both sides of this equation by 9000 to get:
12150 / 9000 = 1 + .07 * n
simplify this to get:
1.35 = 1 + .07 * n
subtract 1 from both sides of the equation to get:
1.35 - 1 = .07 * n
simlify to get:
.35 = .07 * n
divide both sides of the equation by .07 to get:
.35 / .07 = n
solve for n to get:
n = 5
since you now know the value of n, you can substitute in the first equation as follows: