Edexcel International GCSE Mathematics A · 4MA1
Ratio
A ratio compares quantities in a common unit. To divide a total in a given ratio, count the total number of parts, find the value of one part and then scale each share. A part-to-part ratio differs from a part-to-whole fraction.
Key method
For a:b, the first share is a/(a + b) of the total. Convert mixed units before simplifying a ratio.
Worked example
Share 84 in the ratio 2:5.
- The ratio contains 2 + 5 = 7 parts.
- One part is worth 84 ÷ 7 = 12.
- The shares are 2 × 12 and 5 × 12.
Answer and interpretation
24 and 60; the shares add to 84 and simplify to 2:5.
Common mistake
Using 2/5 of 84 confuses the comparison between shares with the fraction of the total.
Practise independently
Simplify 45 minutes : 2 hours.
Check your answer
45:120 = 3:8 after converting hours to minutes.
Syllabus connection
This lesson develops ratio within the number area. Start with the worked method, attempt the independent question without looking at its answer, then explain any correction in your own words. Check the official specification for your tier’s full requirements.
Related resources
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