How To Find RATE In Simple Interest

To find rate in simple interest, you have to know the formula, apply the formula and then simplify to your answer.

In this lesson, you will learn the formula and the step-by-step method for finding rate in simple interest.

BONUS: A link to practice questions on simple interest is included at the end of this lesson.

Formula for finding rate in simple interest

From the general formula for finding simple interest, which is​

I= \frac{PRT}{100}

Change the subject of the formula from (I) to (R) therefore making the rate (R) stand alone to give the formula for finding rate in simple interest.​

R= \frac{100I}{PT}

Question on finding rate in simple interest

Let’s take an example:


If #450 yield #18 in 6 months, find the rate.


List the values given in the question

I = #18

P = #450

R = ??

T = 6 months, which is \dfrac{1}{2} year

NOTE: Time (T) is always calculated in Year.


Transfer the values into the formula

R= \frac{100×18}{450×\frac{1}{2}}


Simplify to your answer

R= \frac{100×18}{225}
  • Multiply the numerators
R= \frac{1800}{225}
  • Divide by the denominator
\frac{1800}{225} = 8


If 450 Naira yield 18 Naira in 6 months, then the Rate is

= 8%

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Click the button to practice questions on simple interest.

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