FAQs on Percentages: Tips and Tricks

Question 1

1. How do I quickly calculate percentage increases and decreases without a calculator?

Accepted Answer

Ans. Use the unitary method: divide the original value by 100 to find 1%, then multiply by the required percentage. For increases, add the result to the original; for decreases, subtract it. Alternatively, multiply the original by 1.2 for a 20% increase or 0.8 for a 20% decrease. These percentage calculation shortcuts save exam time significantly.

Question 2

2. What's the fastest way to find what percentage one number is of another?

Accepted Answer

Ans. Apply the formula: (Part/Whole) × 100. For quick mental math, express the fraction as a decimal first-if 25 out of 200, that's 0.125 or 12.5%. Recognising common fractions (1/4 = 25%, 1/5 = 20%, 1/3 = 33.33%) accelerates percentage conversion problems typical in UPSC CSAT reasoning sections.

Question 3

3. Why do percentage problems in exams trip me up when numbers seem straightforward?

Accepted Answer

Ans. Students often confuse the base value-whether the percentage applies to the original amount or the new amount. Always identify what represents 100% first. Common mistakes include reversing percentage relationships or miscalculating successive percentage changes. Clarifying the reference point before calculating eliminates most percentage errors in competitive exams.

Question 4

4. How do I handle compound percentage changes, like price increases followed by discounts?

Accepted Answer

Ans. For successive percentage changes, multiply the multipliers rather than adding percentages. If a price increases 20% then decreases 10%, calculate 1.2 × 0.9 = 1.08 (8% net increase). This compound percentage approach prevents cumulative errors when multiple increases or decreases occur sequentially in quantitative reasoning questions.

Question 5

5. Which percentage tricks actually save the most time in CSAT, and how do I remember them during exams?

Accepted Answer

Ans. Memorise percentage-to-fraction conversions (20%=1/5, 25%=1/4, 50%=1/2) and the cross-multiplication method for ratio problems. Use mind maps and flashcards to reinforce percentage relationships. Practice percentage problems under timed conditions regularly-these tips prove invaluable when tackling numerical ability sections efficiently during the actual UPSC CSAT examination.

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01:28	Practice Problem – 2
02:20	Question 1
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05:04	Question 2
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07:03	Question 3
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00:07	Practice Problem – 1
01:28	Practice Problem – 2
02:20	Question 1
02:22	Practice Problem – 3
04:21	Practice Problem – 4
05:04	Question 2
05:22	Practice Problem – 5
06:06	Practice Problem – 6
07:03	Question 3
07:08	Practice Problem – 7
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