Simple interest: finding P, R or T
Rearrange I = PRT/100 to find missing principal, rate or time.
Key formulas
What this lesson covers
This lesson builds Secondary 2–3 skill in simple interest rearrange. Read the key formulas, study the worked example, then attempt the written practice and the four-question MCQ review.
Method
Write every step. Name the rule you use (simple interest rearrange) before substituting numbers. Keep units and signs visible until the final sentence.
Common mistakes
Students often rush the sign, use the wrong percentage base, or cancel terms instead of factors. Pause after each line and ask whether the step is reversible.
Exam habit
Underline the question verb (simplify, solve, factorise, find). Box the final answer and, where sensible, substitute back for a quick check.
Worked example
Worked example — simple interest rearrange
Problem. Apply the method for simple interest rearrange with the numbers 7 and 6.
Solution. Identify the rule for simple interest rearrange. Substitute 7 and 6 carefully with signs in brackets if needed. Complete each operation on a new line. State the final answer clearly and check by reversing one step.
Review quiz
1 / 4Warm-up on simple interest rearrange: what is 4+2?
Practice questions
- Practice 1 on simple interest rearrange: compute with the value 25.
- Practice 2 on simple interest rearrange: change the numbers and repeat the same method.
- Practice 3 on simple interest rearrange: write one sentence explaining the key rule.
- Practice 4 on simple interest rearrange: invent a similar exam-style question and solve it.
Study notes
What is the main idea of simple interest rearrange?
Apply the stated formula or rule with clear steps, then check by reversing or substituting.
How should I revise this topic?
Cover the worked example, redo the practice without notes, then complete the MCQ set and log any wrong options.