JKSSB Percentages: Fastest Solving Tricks

Percentage is one of the most scoring topics in the quantitative aptitude section of JKSSB exams.
If your concepts and shortcuts are clear, most questions can be solved within 5–10 seconds.

This guide covers:

• Core percentage concepts
• Important formulas
• Short tricks used in exams
• Solved examples
• Practice questions

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What is Percentage?

Percentage means "per hundred".

$$x\% = \frac{x}{100}$$

Examples:

• $25\% = \frac{25}{100} = 0.25$
• $120\% = 1.20$
• $7\% = 0.07$

Rule: Move the decimal two places to the left.

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Important Conversions to Memorize

Percentage	Fraction	Decimal
50%	1/2	0.5
25%	1/4	0.25
75%	3/4	0.75
20%	1/5	0.20
10%	1/10	0.10
12.5%	1/8	0.125
33.33%	1/3	0.333
66.66%	2/3	0.666

These conversions help you solve many questions mentally.

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Trick 1: Calculate Percentage Using Fractions

Instead of multiplying with decimals, convert percentages into fractions.

Example:
Find $25\%$ of 640

$$25\% = \frac{1}{4}$$ $$640 \times \frac{1}{4} = 160$$

Example:
Find $20\%$ of 450

$$20\% = \frac{1}{5}$$ $$450 \div 5 = 90$$

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Trick 2: Percentage Increase / Decrease

When a value changes from Old to New:

$$\text{Percentage Change} = \frac{\text{Difference}}{\text{Original}} \times 100$$

Example:
Price increases from 200 to 260

$$\frac{260 - 200}{200} \times 100 = \frac{60}{200} \times 100 = 30\%$$

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Trick 3: Successive Increase or Decrease

If a value changes by $a\%$ and then by $b\%$, the net change is:

$$\text{Net Change} = a + b + \frac{ab}{100}$$

Example:
Salary increases by 10% and then by 20%

$$10 + 20 + \frac{10 \times 20}{100}$$ $$= 30 + 2 = 32\%$$

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Trick 4: Price Increase and Consumption Decrease

If price increases by $x\%$, the required decrease in consumption is:

$$\frac{x}{100 + x} \times 100$$

Example:
Price increases by 50%

$$\frac{50}{150} \times 100 = 33.33\%$$

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Trick 5: Interchange Property

Always remember:

$$x\% \text{ of } y = y\% \text{ of } x$$

Example: $20\%$ of 50 = $50\%$ of 20 = 10

This trick saves time in many MCQs.

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Solved Examples (JKSSB Level)

Example 1

Find $35\%$ of 1200.

$$1200 \times 0.35 = 420$$

Answer: 420

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Example 2

If $20\%$ of a number is 50, find $40\%$ of that number.

Let the number be $x$

$$0.2x = 50$$ $$x = 250$$

Now,

$$40\% \text{ of } 250 = 100$$

Answer: 100

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Example 3

A number is increased by 25% and then decreased by 20%. Find net change.

$$a = +25,\quad b = -20$$ $$\text{Net Change} = 25 - 20 + \frac{25 \times (-20)}{100}$$ $$= 5 - 5 = 0\%$$

No net change.

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Practice Questions

Try solving these without calculator:

1. Find $15\%$ of 360
2. If price increases by 25%, find required decrease in consumption
3. If $40\%$ of A = $60\%$ of B, find ratio A:B
4. A salary increases by 20% and then decreases by 10%. Find net change
5. Find $12.5\%$ of 640

(You can publish solutions in a separate post for internal linking.)

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How to Actually Improve Speed

Reading once will not help.
You need deliberate practice.

• Solve 20 percentage questions daily
• Revise formulas every night
• Time yourself (target: under 10 seconds per question)
• Focus on PYQs and mock questions

This is exactly how serious candidates improve.

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