Stacey has earned $9 interest over the past 20 months with an initial investment of $150. What is the simple interest rate she is earning? Express your answer to the nearest tenth of a percent. (It wants me to use the formula I=Prt which I don't remember)

3.6%

Step-by-step explanation:

We are solving the above question, using the simple interest Formula:

I = PRT

Where

I = Interest = $9

P = Principal = $150

R = Interest rate = ??

T = Time in years = 20 months

We convert this to years

12 months = 1 year

20 months = x

x = 20/12

x = 1.67 years

Hence, making R the subject of the formula

R = I/PT

R = 9/150 × 1.67

R = 9/250.5

R = 0.0359281437

Converting to percentage

R = 0.0359281437 × 100

R = 3.59281437%

R = 3.6 %

The simple interest rate she is earning is 3.6%