Worked Example 4: Finding Missing Value
Part of Ratio Basics · GCSE GCSE Mathematics revision
This study notes covers Worked Example 4: Finding Missing Value within Ratio Basics for GCSE Mathematics. Revise Ratio Basics in Number for GCSE Mathematics with 12 exam-style questions and 22 flashcards. This topic appears less often, but it can still be a useful differentiator on mixed-topic papers. It is section 10 of 15 in this topic. Use this study notes to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 10 of 15
Practice
12 questions
Recall
22 flashcards
Worked Example 4: Finding Missing Value
If the ratio of boys to girls is 4:5 and there are 20 boys, how many girls are there?
Solution
Boys : Girls = 4 : 5
20 : ? = 4 : 5
Scale factor: 20 ÷ 4 = 5
Number of girls = 5 × 5 = 25
Answer: 25 girls
Keep building this topic
Read this section alongside the surrounding pages in Ratio Basics. That gives you the full topic sequence instead of a single isolated revision point.
Practice Questions for Ratio Basics
Write the ratio 12:18 in its simplest form.
Explain the difference between the ratio 3:5 and the ratio 5:3.
Quick Recall Flashcards
12 questions on Ratio Basics — practise free
Instant marking, adaptive difficulty, and 22 spaced repetition flashcards. Free until your GCSEs.
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