Rounding to decimal places

2026-11-05Numbers & Estimation Ms Chu

Round to 1, 2 or 3 decimal places using the next-digit rule.

Key formulas

\text{Look at the next digit}; 5 \text{or more rounds up}

What this lesson covers

This lesson builds Secondary 2–3 skill in decimal places. 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 (decimal places) 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 — decimal places

Problem. Apply the method for decimal places with the numbers 7 and 6.

Solution. Identify the rule for decimal places. 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 / 4

Warm-up on decimal places: what is 6+5?

Practice questions

Practice 1 on decimal places: compute with the value 13.
Practice 2 on decimal places: change the numbers and repeat the same method.
Practice 3 on decimal places: write one sentence explaining the key rule.
Practice 4 on decimal places: invent a similar exam-style question and solve it.

Study notes

What is the main idea of decimal places?

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.