Question

Safiya deposited money into a bank account that earned 6.5% simple interest each year. After 312 years, she had earned $36.40 in interest on the account.

No other money was deposited into or withdrawn from the account.

How much was her initial deposit?

Answer 1

Answer: If the time is 3 1/2 years (most reasonable assumption)

Her initial deposit was $160

Step-by-step explanation:  The basic formula for simple interest is

i = prt  i is interest, P is principal (deposit) r is the percentage (converted to a decimal) and t is time, the number of years.

For this question, you have to rearrange the equation to solve for p.

So divide both sides by rt and you have

p =  i/rt

Substitute the values given

p = 36.40/(0.065)(3.5)