Question

The simple interest formula is ​I=Prt ​, where I is the interest, P is the principal, r is the interest rate, and t is the time. How long would it take to have $1335.60 in interest if the principal is $5300 and the interest rate is 7.2%?

Answer 1

t = 5.3 years
(about 5 years 4 months)

Equation:
t = (1/r)(A/P - 1)
Calculation:
First, converting R percent to r a decimal
r = R/100 = 7.2%/100 = 0.072 per year,
then, solving our equation

t = (1/0.072)((4835.6/3500) - 1) = 5.3
t = 5.3 years