Percentage Questions for SSC CHSL

What is Percentage

Percentage means 'out of 100'. When we say 40%, we mean 40 out of every 100 parts. It is a way to compare quantities on a common scale. Converting between fractions, decimals, and percentages is the first skill you need to master because SSC CHSL often gives values in one form and expects answers in another.

• To convert fraction to percent: multiply by 100. Example: 3/4 = 75%
• To convert percent to fraction: divide by 100. Example: 35% = 35/100 = 7/20
• To convert percent to decimal: move decimal two places left. 45% = 0.45
• Learn fraction-to-percent equivalents up to 1/12 by heart — saves 30 seconds per question
• x% of y = y% of x — this symmetry trick is very useful in calculation shortcuts

Percentage Increase and Decrease

SSC CHSL loves questions where a value goes up or down by a certain percent. The key formula uses the original value as the base (denominator), not the new value. A very common trap is using the new value as the base — always go back to the original.

• Increase%: ((New - Old) / Old) x 100
• Decrease%: ((Old - New) / Old) x 100
• If price increases by r%, to restore original: decrease by (r / (100+r)) x 100 percent
• If price decreases by r%, to restore original: increase by (r / (100-r)) x 100 percent
• Multiplier method: 20% increase means multiply by 1.2; 20% decrease means multiply by 0.8

Successive Percentage Change

When a value changes by two percentages one after the other (like two years of growth, or a double discount), you cannot simply add the percentages. There is an interaction effect. SSC CHSL tests this in population problems, discount chains, and price hike scenarios. The net effect formula saves time over multiplying step by step.

• Two successive changes of a% and b% give net change: a + b + (ab/100) percent
• If both are increases, ab is positive — net change is more than simple addition
• If one is increase and other decrease, use negative sign for the decrease
• If both are decreases, result is less than simple subtraction
• Multiplier method is safest: apply 1.a then 1.b sequentially on the original

Key Fraction-Percent Equivalents to Memorise

SSC CHSL questions often have numbers that are exact fractions of each other. Knowing these by heart lets you skip division entirely. This table is your speed weapon in the exam hall.

• 1/2 = 50%, 1/3 = 33.33%, 1/4 = 25%, 1/5 = 20%
• 1/6 = 16.67%, 1/7 = 14.28%, 1/8 = 12.5%, 1/9 = 11.11%
• 1/10 = 10%, 1/11 = 9.09%, 1/12 = 8.33%
• 2/3 = 66.67%, 3/4 = 75%, 2/5 = 40%, 3/5 = 60%, 4/5 = 80%
• These also help in Profit-Loss and Ratio topics which share the same base numbers

• Using new value as the base instead of original value in percentage change problems — always put OLD value in denominator
• Simply adding two successive percentages: 10% + 20% is NOT 30% when applied one after the other on same value
• Confusing 'percent more than' with 'percent of': 'A is 25% more than B' means A = 1.25B, not A = 0.25B
• In reverse percent problems (restore to original), students use the same percent — remember price up 25% needs 20% cut to restore, not 25%
• Not reading whether the question asks for the increase amount or the final value — re-read the last line of the question

• OLD is GOLD: In percent change, Old value always goes in the denominator. Old = Gold = Base.
• For successive change formula a + b + ab/100: think ADD, ADD, then ADD their PRODUCT divided by 100. Three additions.
• Reverse percent trick: Up by r? Come down by r/(100+r). Down by r? Go up by r/(100-r). The denominator flips sign.
• Fraction table song pattern: 1/2, 1/4, 1/8 are the halving family: 50, 25, 12.5. Each is half the previous.

• SSC CHSL typically puts 1-2 direct percentage questions and 2-3 more in Profit-Loss or DI — so mastering percentage doubles your payoff across sections
• Questions are mostly one-step or two-step — rarely complex chains of more than two changes. If your calculation is getting very long, you are likely using the wrong approach
• Population/price increase over years is a favourite question type — set up the multiplier (1 + r/100) and apply it; do not recalculate base each time
• In DI (Data Interpretation) sets, percentage change between two years is almost always asked — practice reading bar graph values and applying the percent change formula fast
• Time allocation: a straightforward percentage question should take 45-60 seconds. If it crosses 90 seconds, mark and move — do not let one question eat your time