17 out of 20
= 85%
21 out of 25
= 84%
Learn the 3-Step Method
1Turn each score into a fraction.
Maya: 17/20. Leo: 21/25.
2Convert both to percentages.
17/20 = 85/100 = 85%. 21/25 = 84/100 = 84%.
3Compare the percentages.
Now the totals match (100), the comparison is fair.
Worked Example
Class A: 27 of 30 passed. Class B: 22 of 25 passed. Which class did better?
Watch Out! Common Mistakes
Wrong! The tests had different totals. As percentages: Maya 85%, Leo 84%.
Wrong! 3 out of 30 ≠ 3 out of 25. Convert to percentages: 90% vs 88%.
Careful! Keep exact values until the comparison is done — 85 beats 84.
⬇ Cheat Sheet
- Different totals? Never compare raw scores.
- Convert each to a percentage.
- Compare the percentages.
- Keep exact values — don't round early.
📖 Continue Your Journey
Quick summary
- Scores with different totals can't be compared directly.
- Convert each to a percentage first: 17/20 = 85%, 21/25 = 84%.
- Then compare like for like: 85% beats 84%.
- Don't round until the comparison is finished.
Frequently asked questions
Why convert to percentages before comparing?
Because percentages put both scores out of the same total (100), making the comparison fair — 21/25 looks bigger than 17/20 but is actually the smaller proportion.
Which is better: 27 out of 30 or 22 out of 25?
27/30 = 90% and 22/25 = 88%, so 27 out of 30 is the better result.
Where else does this idea appear?
League tables, survey results, discounts, nutrition labels — anywhere quantities have different totals, percentages make them comparable.
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