Question

The formula for simple interest is I = Prt where P is the principal(starting amount), r is the interest rate(as a decimal), and t is time.

Solve the formula for r.
A. r = I / (Pt)
B. r = I / (Pr)
C. r = Pt / I
D. r = I / (P + t)

Answer 1

To solve for the interest rate r in the simple interest formula I = Prt, divide the interest I by the product of the principal P and time t. Thus, the correct answer is r = I / (Pt) which corresponds to option A.

Step-by-step explanation:

To solve the formula for simple interest I = Prt for r, the interest rate, you would take the following steps:

• First, understand the formula: I = Prt which stands for Interest equals Principal times rate times time.
• To isolate r, you want to get rid of the other variables that are being multiplied with it, which are P for principal and t for time.
• Divide both sides of the equation by Pt to isolate r: I / Pt = r.

Therefore, the correct answer is A. r = I / (Pt)

Using an example from above, if you deposit $100 at a simple interest rate of 5% for one year, the simple interest would be calculated as:

$100 × 0.05 × 1 = $5

The rate r here is represented as 0.05, proving the simple interest rate calculation method.