Quantitative aptitude is tested in every campus placement drive in India. Whether you are preparing for TCS NQT, AMCAT, Infosys, Wipro, or Accenture, speed and accuracy directly decide whether you clear the cut-off. Most placement tests allow 60 to 90 seconds per question — students who use long methods consistently run out of time.
1. Percentage Cross-Calculation Trick
X% of Y always equals Y% of X. Example: 16% of 25 = 25% of 16 = 4. This single trick eliminates lengthy multiplication for dozens of placement questions every year.
2. Multiply Any Number by 11
Add the two digits of the number and place the sum in the middle. Example: 63 × 11 — add 6 + 3 = 9, result is 693. If the sum exceeds 9, carry the 1 to the left digit: 75 × 11 = 7_(7+5)_5 = 7_12_5 = 825.
3. Fraction-to-Percentage Memory Table
Memorise these: 1/6 = 16.67%, 1/7 = 14.28%, 1/8 = 12.5%, 1/9 = 11.11%, 1/11 = 9.09%, 1/12 = 8.33%. These appear in at least 3 to 4 questions in every placement aptitude test.
4. LCM Method for Time and Work
Assign total work as the LCM of all given days. Convert each person’s rate to units per day, then add rates for combined work. This eliminates all fraction arithmetic — especially effective for 3-person work problems.
5. Ratio Chaining Shortcut
For A:B = 2:3 and B:C = 4:5, multiply across to get A:B:C = 8:12:15. Works for any number of chained ratios and is significantly faster than cross-multiplication.
6. Speed-Distance Unit Conversion
To convert km/h to m/s, multiply by 5/18. To convert m/s to km/h, multiply by 18/5. Always convert units before applying the formula. Forgetting this step is one of the top reasons for wrong answers in speed-distance questions.
7. 2-Year Compound Interest Formula
CI for 2 years = P × r/100 × (2 + r/100). This bypasses the year-by-year calculation entirely. For 3 years, apply the standard formula CI = P[(1 + r/100)³ − 1] but compute step by step using the 2-year result as a shortcut for the first two years.
8. Trailing Zeros in Factorial
Count factors of 5: add n/5 + n/25 + n/125 (ignore remainders). Example: 100! has 100/5 + 100/25 + 100/125 = 20 + 4 + 0 = 24 trailing zeros. This exact question appears in TCS NQT and AMCAT regularly.
9. Divisibility Quick Rules
Divisible by 8: last 3 digits divisible by 8. By 11: difference of alternating digit sums divisible by 11. By 7: double the last digit, subtract from the remaining number, check divisibility. These rules save 30 to 40 seconds per number-system question.
10. Average of Consecutive Numbers
The average of any arithmetic sequence is always the middle value (or mean of the two middle values for even-count sets). Never add and divide — identify the middle term directly.
How to Use These Shortcuts Effectively
Knowing a shortcut and applying it under exam pressure are two different skills. Practice each shortcut in timed drills — 20 questions in 15 minutes — until it becomes reflexive. Use Campus Achievers’ mock tests to practice under real placement exam conditions and track your improvement over time.