In a placement aptitude test, speed is as important as accuracy. Most tests allow only 60–90 seconds per question. These 30 shortcuts will help you solve common question types in 15–25 seconds instead of a minute or more.

Percentage Shortcuts

Shortcut 1: Percentage Change Formula

Instead of computing base → new → percentage, use: % change = (difference ÷ original) × 100

Example: Price rises from 80 to 100. % change = (20 ÷ 80) × 100 = 25%

Shortcut 2: Successive Percentage Changes

If a value changes by A% and then B%, net change = A + B + (AB/100)

Example: 20% increase then 10% increase = 20 + 10 + (20×10/100) = 32% net increase

Shortcut 3: Percentage to Fraction Conversions (Memorise These)

  • 10% = 1/10, 12.5% = 1/8, 16.67% = 1/6
  • 25% = 1/4, 33.33% = 1/3, 50% = 1/2
  • 75% = 3/4, 20% = 1/5, 40% = 2/5

Ratio and Proportion Shortcuts

Shortcut 4: Componendo-Dividendo

If a/b = c/d, then (a+b)/(a-b) = (c+d)/(c-d). Useful for ratio comparison problems.

Shortcut 5: Ratio Comparison Without Common Denominator

To compare a/b vs c/d: compare a×d vs b×c. Larger product = larger ratio.

Time, Speed, and Distance Shortcuts

Shortcut 6: Average Speed for Equal Distances

If you travel distance D at speed S1 and return at S2, average speed = 2S1S2/(S1+S2)

Never add and divide — this is the most common mistake in placement exams.

Shortcut 7: Relative Speed

  • Same direction: relative speed = |S1 – S2|
  • Opposite direction: relative speed = S1 + S2

Shortcut 8: Train Problems

Time for a train of length L to cross a stationary object of length l = (L + l) / speed. For a point object, l = 0.

Shortcut 9: Time to Cross Another Train

Time = (L1 + L2) / (S1 + S2 if opposite, S1 – S2 if same direction)

Time and Work Shortcuts

Shortcut 10: Work Rate Formula

If A does work in 'a' days and B in 'b' days, together they finish in ab/(a+b) days.

Shortcut 11: Efficiency Method

Assume total work = LCM of individual times. Each person's daily rate = total work ÷ their days. Add rates for combined work.

Shortcut 12: Work Done in N Days

Work done = N × (combined daily rate). Remaining work = Total – Work done.

Number System Shortcuts

Shortcut 13: Divisibility Rules (Memorise)

  • Div by 3: sum of digits divisible by 3
  • Div by 4: last 2 digits divisible by 4
  • Div by 8: last 3 digits divisible by 8
  • Div by 9: sum of digits divisible by 9
  • Div by 11: alternating sum divisible by 11

Shortcut 14: Unit Digit Cycles

  • 2: 2, 4, 8, 6 (cycle of 4)
  • 3: 3, 9, 7, 1 (cycle of 4)
  • 7: 7, 9, 3, 1 (cycle of 4)
  • 4 and 9: cycle of 2 (4,6 and 9,1)
  • 5 and 1: always 5 and 1

Useful for: What is the unit digit of 7^63? Power 63 = 4×15+3, so unit digit = 3rd in cycle = 3.

Shortcut 15: HCF and LCM Relationship

For any two numbers a and b: HCF × LCM = a × b.

Profit and Loss Shortcuts

Shortcut 16: Selling Price Formula

SP = CP × (100 + profit%) / 100 or CP × (100 – loss%) / 100

Shortcut 17: CP from SP and Profit%

CP = SP × 100 / (100 + profit%)

Shortcut 18: Dishonest Shopkeeper Problems

If a shopkeeper declares X% profit but uses faulty weights measuring (actual – shortage)g as (actual)g: True profit% = (declared% × actual + shortage × 100) / (actual – shortage)

Simple and Compound Interest Shortcuts

Shortcut 19: Simple Interest

SI = PRT/100 where P = principal, R = rate%, T = time in years

Shortcut 20: Compound Interest (Annual)

CI = P(1 + R/100)^T – P. For small rates and short durations, CI ≈ SI + SI²/P.

Shortcut 21: Difference Between CI and SI (2 years)

Difference = P×(R/100)²

Mixtures and Alligation

Shortcut 22: Alligation Rule

To mix two items of prices A and B to get price C: ratio = (B-C):(C-A)

Permutations and Combinations

Shortcut 23: Circular Arrangements

Arranging n people in a circle = (n-1)! not n!

Shortcut 24: Arrangements with Identical Items

n items with a identical and b identical: arrangements = n! / (a! × b!)

Data Interpretation Shortcuts

Shortcut 25: Quick % Calculation in DI

For X% of Y: 10% of Y = Y/10. Then build up. Example: 35% of 840 = 84×3 + 42 = 252 + 42 = 294.

Shortcut 26: Growth Rate in DI

If value goes from V1 to V2, growth = (V2-V1)/V1 × 100. Do this mentally by finding the difference.

Logical Reasoning Shortcuts

Shortcut 27: Venn Diagram (3 sets)

Total = A + B + C – (A∩B) – (B∩C) – (A∩C) + (A∩B∩C)

Shortcut 28: Calendar Problems

Odd days pattern: January=3, Feb=0(non-leap)/1(leap), March=3, April=2, May=3, June=2, July=3, Aug=3, Sep=2, Oct=3, Nov=2, Dec=3.

General Exam Strategy

Shortcut 29: First-Pass Strategy

Attempt all easy questions first (30 seconds each). Mark difficult ones and return if time allows. Never spend more than 90 seconds on one question.

Shortcut 30: Elimination Before Guessing

Before guessing, eliminate at least 2 options using logical reasoning. This raises your probability from 25% to 50%.

FAQ: Aptitude Shortcuts for Placement

Q: How many shortcuts should I memorise for placement tests?

A: Focus on the 10–15 most frequently tested topics for your target companies. Quality of recall under time pressure matters more than quantity memorised.

Q: Do all placement tests have negative marking?

A: Not all. TCS NQT has no negative marking in foundation; Wipro does not officially confirm. Always check the specific test guidelines before attempting.