Find the annual interest rate. I=$54, P=$900, t=18 months

Question

I need help with this answer

Answer 1

Interest=Principal x Rate x Time (in years)

Interest=$54

Principal=$900

Convert 18 months to years by dividing by 12 (there are 12 months in a year) so

Time = 18/12=1.5

Plug into formula you get

54=(900)R(1.5)

54=1350R

Divide by 1350

.04=R

Annual Rate is 4%