Question

you put $400 in an account. the account earns $18 simple intrest in 9 months. what is the anual interest rate?

Answer 1

Use the formula,

I = Prt

P = Principal amount = 400

I = interest = 18

r = annual rate

t = time in years = 9/12 = 3/4

so,

18 = 400*r*3/4

r = 0.06

so the annual interest rate is 0.06 or 6%

Answer 2

6%

Explanation:

I = Prt, so r = I / (Pt)

t = 9 months / 12 months = 0.75

r = $18 / ($400 * 0.75) = 0.06, or 6%