Best quantitative aptitude shortcuts for SBI PO prelims

SBI PO Quantitative Aptitude is not only a test of whether you can solve a calculation. It is a test of how quickly you can recognize the right calculation and finish it without wasting time on unnecessary arithmetic.

That makes mental-math shortcuts extremely useful. Percentages, fractions, ratios, averages, approximation, multiplication, division, and common arithmetic patterns appear again and again across quantitative aptitude questions. The goal is not to memorize dozens of tricks. It is to make a small set of reliable shortcuts automatic.

1. Build percentages from easy fractions

Percentage calculation is one of the most reusable skills in quantitative aptitude. Instead of calculating a percentage from scratch every time, memorize the common fraction-to-percentage conversions.

• 1/2 = 50%
• 1/4 = 25%
• 1/5 = 20%
• 1/10 = 10%
• 1/20 = 5%
• 1/25 = 4%
• 1/50 = 2%
• 1/100 = 1%

For example, if you need 25% of 840, do not multiply by 25 and divide by 100.

The same idea works backwards. If a question asks what percentage 120 is of 480:

2. Use the 10% and 1% building blocks

When a percentage is not a familiar fraction, build it from 10% and 1%. These two values are easy to calculate mentally.

This is often faster than using the formal percentage formula.

3. Convert percentage changes into ratios

Percentage increase and decrease questions become much easier when you think in terms of the original value and the change.

For mental calculation, ask what fraction the change represents before doing anything complicated.

This shortcut becomes especially useful in profit/loss, discount, data comparison, and number-based word problems.

4. Simplify ratios before calculating

Never divide large numbers directly when a ratio can first be reduced.

Both numbers are divisible by 240, so the complicated-looking ratio becomes a simple one immediately.

For larger numbers, first look for common factors such as 2, 5, 10, 20, 50, or 100. Reducing the ratio before working with it can eliminate an entire calculation.

5. Find averages using deviations

When numbers are clustered around a convenient value, do not add every number from scratch. Choose a base, calculate the deviations, and adjust.

This method becomes even more useful when the numbers are large but close together.

6. Approximate before doing long division

Approximation is one of the most useful time-saving habits in timed exams. Before dividing, ask whether the numbers are close to convenient values.

The same technique works with percentages and ratios.

Approximation is especially useful when the answer choices are clearly separated. When two options are very close, switch to a more precise calculation instead.

7. Multiply numbers close to 100

If both numbers are close to 100, use deviations instead of ordinary multiplication.

The same base idea works for numbers above 100.

Use this when the numbers are naturally close to 100. There is no reason to force the method on numbers that are not.

8. Use fast multiplication patterns

Some multiplication questions have a built-in shortcut. For example, multiplying a two-digit number by 11 can often be done mentally by adding its digits between the original digits.

For a number such as 68 × 11:

When the middle sum is 10 or more, carry normally.

Recognizing these patterns saves time that would otherwise be spent on standard multiplication.

9. Break difficult division into easier factors

If a divisor can be factored into simple numbers, divide step by step.

The point is to replace one awkward division with two easier ones.

This technique is particularly useful when the divisor has convenient factors such as 4, 5, 6, 8, 9, 10, or 12.

10. Use algebraic identities for squares

You do not need a separate long calculation for every square. Use a nearby round number when it makes the arithmetic easier.

For numbers ending in 5, there is an even faster shortcut.

So 65² = 4,225.

11. Recognize when not to calculate exactly

This is one of the most important exam habits. A fast solver does not calculate everything to the last digit automatically.

Before starting a calculation, ask:

• Does the question ask for an approximate value?
• Are the answer choices far apart?
• Can I compare the values without finding the exact answer?
• Can I simplify the fraction or ratio first?
• Is there a familiar percentage or multiplication pattern here?

Often the real shortcut is deciding what calculation you can avoid.

12. Use a question-selection strategy

Quantitative aptitude is also about choosing the right order of attack. During a timed section, calculation-heavy questions should not automatically become your first targets.

Look first for questions where the method is immediately visible: simple percentages, direct ratios, basic averages, familiar multiplication, approximation, or short arithmetic. Leave questions that require several long calculations until you have already collected the easier marks available to you.

A compact SBI PO shortcut checklist

• Memorize common fractions as percentages.
• Use 10% and 1% to build unfamiliar percentages.
• Reduce ratios before calculating.
• Use deviations for averages of nearby numbers.
• Approximate awkward divisions when the options allow it.
• Use base-100 multiplication for numbers close to 100.
• Recognize instant patterns such as ×11 and squares ending in 5.
• Factor difficult divisors before dividing.
• Compare answer choices before doing unnecessary exact arithmetic.
• Skip calculations that are taking too long and return later when appropriate.

How to practise these shortcuts

Shortcuts become useful only when they become automatic. Reading ten tricks once will not improve your speed. Practice the same patterns repeatedly until the setup takes only a few seconds.

A good practice session can be simple: spend a few minutes on percentages, then multiplication, division, averages, ratios, and approximation. After that, solve mixed questions under a timer so you learn to recognize which shortcut applies without being told.

The aim is not to solve every SBI PO Quantitative Aptitude question using a trick. The aim is to recognize the easy calculation hidden inside a difficult-looking question and finish it with as little arithmetic as possible.