Percentage Tricks and Shortcuts: Questions with Solutions for SSC CGL, CHSL, MTS (Maths)

Percentage is the base of profit and loss, interest, data interpretation and many other chapters of SSC maths, so a strong grip on it saves a lot of time in the exam. These percentage tricks for SSC explain the fraction table, the multiplier method and the successive change rule, and solve the popular question types (population, marks, election and price change) step by step.

What Is a Percentage?

Percent means "per hundred". x% means x / 100. To find a percentage: (Part / Whole) × 100.

Fraction and Percentage Table (Learn by Heart)

The Multiplier Method

Do not calculate the increase and then add it. Use a single multiplier.

Successive Change

For two changes of a% and b%, the net change = a + b + ab/100 (use a minus sign for a decrease). An increase of r% followed by a decrease of r% gives a net decrease of r²/100 %.

Solved Examples

Example 1. Find 35% of 240.
35/100 × 240 = 84.

Example 2. A number is increased by 20% and then decreased by 20%. What is the net change?
Net change = 20 − 20 − (20 × 20)/100 = −4. The number decreases by 4% (100 → 120 → 96).

Example 3. A salary is increased by 10% and then by 20%. Find the net increase.
10 + 20 + (10 × 20)/100 = 30 + 2 = 32%.

Example 4 (population). The population of a town is 50,000. It increases by 10% every year. What will it be after 2 years?
50,000 × 1.1 × 1.1 = 60,500.

Example 5 (marks). A student needs 40% marks to pass. He gets 120 marks and fails by 40 marks. Find the total marks.
Pass marks = 120 + 40 = 160. This is 40% of the total, so the total = 160 ÷ 0.4 = 400.

Example 6 (election). In an election of two candidates, A gets 60% of 5,000 votes. How many votes does B get (no invalid votes)?
B gets 40% of 5,000 = 2,000.

Example 7 (price and consumption). The price of an item rises by 25%. By how much % should the consumption fall so that the expense is the same?
25 / (100 + 25) × 100 = 20%.

Useful Tricks

• x% of y = y% of x. So 20% of 50 = 50% of 20 = 10.
• To find 15% of a number, find 10% and add its half.
• If A is x% more than B, then B is x/(100 + x) × 100 % less than A.
• If a number is increased by 50% and decreased by 50%, the result is 25% less than the original.

Quick Tips

• Learn the fraction and percentage table, and the multipliers.
• Use x% of y = y% of x to make a hard question easy.
• Use the successive change formula and do not calculate twice.
• For marks questions, find the pass marks first.

Quick Revision Points

• x% = x/100 and Percentage = (Part / Whole) × 100.
• Net change = a + b + ab/100.
• A rise of r% and a fall of r% give a net fall of r²/100 %.
• Increase by 20% means multiply by 1.2.
• x% of y = y% of x.

Practice Questions With Answers

1. Find 25% of 480.
   Answer: 120
2. 40 is what percent of 250?
   Answer: 16%
3. Increase 80 by 25%.
   Answer: 100
4. Decrease 200 by 15%.
   Answer: 170
5. A salary is increased by 20% and then by 10%. Find the net increase.
   Answer: 32%
6. The price of sugar rises by 20%. By what percent must the consumption fall to keep the expense the same?
   Answer: 16 and 2/3 %
7. A is 25% more than B. B is how much percent less than A?
   Answer: 20%
8. Pass marks are 35% of 600. Find the pass marks.
   Answer: 210
9. A number increased by 10% becomes 220. Find the number.
   Answer: 200
10. Write 0.5 as a percentage.
    Answer: 50%

How to Practise This Chapter

Practise 10 questions every day and write the steps on paper. Then attempt timed sets from our practice papers and the previous year papers page. See all topics on the Mathematics notes page and the next topic Profit, Loss and Discount. Formulas are in the Formula Guide and more practice is in the Quantitative Aptitude notes.

Frequently Asked Questions

What is percentage?

Percentage is a number written as a fraction of 100.

How do I find x percent of a number?

Multiply the number by x/100.

What is the multiplier method?

It is a method in which an increase of r% is a multiplication by (100 + r)/100, and a decrease by (100 − r)/100.

What is the successive percentage change formula?

Net change = a + b + ab/100.

What happens when a number is increased and decreased by the same percent?

There is a net decrease of r squared divided by 100 percent.

How do I find the consumption change when the price rises?

Reduce the consumption by x/(100 + x) × 100 percent.

Which fractions should I learn as percentages?

1/2 to 1/12, and 1/15, 1/16 and 1/20.

Is percentage asked in SSC exams?

Yes. Percentage questions are asked directly and inside data interpretation, profit and loss and interest.

How can I calculate percentage faster?

Use the fraction table and the multiplier method.

What are the common mistakes?

Taking the percentage of the wrong base number, and adding successive percentages directly.

How much time should I take for a percentage question?

About 30 to 40 seconds.

What is the difference between percent and percentage points?

If a rate rises from 10% to 15%, it rises by 5 percentage points, but by 50% in relative terms.