Percentage error and approximate values
Compute percentage error from true and approximate values.
Key formulas
What this lesson covers
This lesson builds Secondary 2–3 skill in percentage error. 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 (percentage error) 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 — percentage error
Problem. Apply the method for percentage error with the numbers 4 and 3.
Solution. Identify the rule for percentage error. Substitute 4 and 3 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 percentage error: what is 8+4?
Practice questions
- Practice 1 on percentage error: compute with the value 22.
- Practice 2 on percentage error: change the numbers and repeat the same method.
- Practice 3 on percentage error: write one sentence explaining the key rule.
- Practice 4 on percentage error: invent a similar exam-style question and solve it.
Study notes
What is the main idea of percentage error?
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.