Problem
You deposit $4 into a bank account paying 5% simple interest per month. You left the money in for 3 years. Find the interest earned and the amount at the end of those 3 years?
Result
The interest is $7.2 and the amount is $11.2.
Explanation
STEP 1: Convert interest rate of 5% per month into rate per year.
rate per year = rate per month⋅12=5%⋅12=60%STEP 2: Find an interest by using the formula I=P⋅i⋅t, where I is interest, P is total principal, i is rate of interest per year, and t is total time in years.
In this examplee P = $4, i = 60% and t = 3 years, so
III=P⋅i⋅t=4⋅0.6⋅3=7.2STEP 3: Find an amount by using the formula A=P+I.
Since P = $4 and I = $7.2 we have
AAA=P+I=4+7.2=11.2