Percentages — Basics
Ten exam-style percentage questions — fast fraction conversions, percentage change, and the discount and consumption traps every placement paper loves.
One question at a time — answer, learn from the explanation, and keep your combo alive. Stuck? You have two 50:50s and one hint (each halves that question's XP).
Practice sheet: all 10 questions
Prefer reading first? Every question from this quiz, with the answer and a worked explanation. (Solving them in the quiz above earns XP — up to ≈95.)
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Q1. What is 25% of 480?
- a. 110
- b. 120
- c. 125
- d. 130
Show answer & explanation
Answer: B. 120
25% is the same as one quarter. 480 ÷ 4 = 120. Converting common percentages to fractions (25% = 1/4, 20% = 1/5, 12.5% = 1/8) is the fastest way to do these in your head.
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Q2. A number increases from 80 to 100. What is the percentage increase?
- a. 20%
- b. 25%
- c. 30%
- d. 80%
Show answer & explanation
Answer: B. 25%
Percentage change is always measured against the ORIGINAL value: (100 − 80) ÷ 80 × 100 = 25%. The classic trap is dividing by the new value (20 ÷ 100 = 20%) — exam setters almost always include that as an option.
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Q3. A shirt priced at ₹800 is sold at a 15% discount. How much does the buyer pay?
- a. ₹640
- b. ₹660
- c. ₹680
- d. ₹700
Show answer & explanation
Answer: C. ₹680
15% of 800 = 120, so the price is 800 − 120 = ₹680. Quicker: paying after a 15% discount means paying 85%, and 0.85 × 800 = 680 in one step.
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Q4. In a class of 60 students, 45% are girls. How many boys are in the class?
- a. 27
- b. 30
- c. 33
- d. 36
Show answer & explanation
Answer: C. 33
If 45% are girls, 55% are boys: 0.55 × 60 = 33. Jumping straight to the percentage the question actually asks about (boys, not girls) saves a subtraction — and avoids picking 27, the count of girls.
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Q5. A value is increased by 20% and the result is then decreased by 20%. What is the net change?
- a. 0% — it returns to the original
- b. 2% decrease
- c. 4% decrease
- d. 4% increase
Show answer & explanation
Answer: C. 4% decrease
Successive changes multiply: 1.20 × 0.80 = 0.96, a 4% net decrease. Equal up-and-down percentage moves never cancel — the shortcut for ±x% is a net change of −x²/100, here −(20²)/100 = −4%.
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Q6. If 30% of a number is 90, what is 45% of the same number?
- a. 120
- b. 135
- c. 145
- d. 150
Show answer & explanation
Answer: B. 135
30% → 90 means the number is 300, and 45% of 300 = 135. Even faster: 45% is 1.5 times 30%, so the answer is 1.5 × 90 = 135 without ever finding the number.
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Q7. A student scores 380 marks out of 500. What is the score as a percentage?
- a. 72%
- b. 74%
- c. 76%
- d. 78%
Show answer & explanation
Answer: C. 76%
380 ÷ 500 × 100 = 76%. With a base of 500, each 5 marks is exactly 1% — so 380 marks is 380 ÷ 5 = 76%. Spotting friendly bases (500, 200, 50, 25) turns division into a one-liner.
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Q8. The price of sugar rises by 25%. By what percentage must a family reduce its consumption so that its spending on sugar stays the same?
- a. 20%
- b. 25%
- c. 30%
- d. 15%
Show answer & explanation
Answer: A. 20%
Spending = price × quantity. If price becomes 5/4, quantity must become 4/5 to keep the product constant — a drop of 1/5 = 20%. General rule: for an x% rise, the cut needed is x/(100+x) × 100, here 25/125 × 100 = 20%. Answering 25% is the standard trap.
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Q9. Which of the following equal 36? Select all that apply.
- a. 30% of 120
- b. 45% of 80
- c. 24% of 150
- d. 18% of 210
Show answer & explanation
Answer: A. 30% of 120 · B. 45% of 80 · C. 24% of 150
30% of 120 = 36 ✓; 45% of 80 = 36 ✓; 24% of 150 = 36 ✓; but 18% of 210 = 37.8 ✗. Useful identity for checking quickly: a% of b always equals b% of a (45% of 80 = 80% of 45 = 36).
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Q10. A phone's price drops from ₹20,000 to ₹17,000. What is the percentage decrease? Enter the number only.
Show answer & explanation
Answer: 15
The decrease is ₹3,000 on an original price of ₹20,000: 3000 ÷ 20000 × 100 = 15%. As always with percentage change, divide by the ORIGINAL value (20,000), not the new one.