Railway recruitment exams, like those for RRB NTPC, Group D, and ALP, are highly competitive and time-bound. A significant portion of these exams is dedicated to Mathematics and General Intelligence & Reasoning. To clear the cut-off, it’s not enough to know how to solve a problem; you must solve it accurately and quickly. This guide is your ticket to mastering speed math, a skill that will help you gain a crucial edge over the competition.

1. The Absolute Basics: Memorize and Internalize

Before applying any advanced tricks, you must be fluent in the basics. This foundation is non-negotiable for rapid calculation.

Core Fundamentals to Master:

  • Multiplication Tables: Up to 30.
  • Squares: Up to 50.
  • Cubes: Up to 20.
  • Fractions & Percentages: Common conversions (1/3 ≈ 33.33%, 3/4 = 75%, etc.).

Having these on the tip of your fingers will prevent you from wasting time on simple arithmetic.

2. Rapid Multiplication Tricks

Multiplication is a constant in railway exams. Master these to save significant time.

A. Multiplication by 11

A simple and elegant trick that works every time.

Example: 35 × 11

Step 1: Write the first and last digits (3 and 5) with a space in between: 3 _ 5.
Step 2: Add the two digits and place the sum in the middle: 3 + 5 = 8.
Step 3: Combine them.

Answer: 385

B. Criss-Cross Multiplication for Two-Digit Numbers

This Vedic math technique is perfect for multiplying any two 2-digit numbers mentally.

Example: 24 × 32

  • Step 1: Multiply the last digits. 4 × 2 = 8. (Last digit is 8).
  • Step 2: Criss-cross and add. (2 × 2) + (4 × 3) = 4 + 12 = 16. Write down 6, carry over 1.
  • Step 3: Multiply the first digits. 2 × 3 = 6. Add the carried over 1: 6 + 1 = 7. Write down 7.

Answer: 768

3. Squaring and Cube Roots

Being fast with squares and roots can significantly reduce your problem-solving time.

A. Squaring Numbers Near a Base

Use the formula (a + b)² = a² + 2ab + b² for numbers like 51 or 48.

Example: 48²

Think of 48 as (50 − 2).
48² = (50 − 2)² = 50² − (2 × 50 × 2) + 2²
= 2500 − 200 + 4
= 2304

B. Finding Cube Roots in Seconds

This method is a magical shortcut for finding the cube root of a perfect cube.

Example: Find ∛1728

Step 1: The last digit is 8. This means the cube root's last digit must be 2 (since 2³ = 8).

Step 2: Ignore the last three digits (728). The remaining number is 1.

Step 3: Find the largest cube less than or equal to 1. That's 1 (1³). So the first digit is 1.

Answer: 12

4. Smart Percentages and Fractions

Questions involving percentages, profit & loss, and simple/compound interest can be solved much faster using fractional equivalents.

Example: Find 25% of 1200, then add 16.67% of 600

25% = 1/4 ⇒ (1/4) × 1200 = 300
16.67% ≈ 1/6 ⇒ (1/6) × 600 = 100

Sum = 300 + 100 = 400

5. Time-Saving Strategies for the Exam Hall

Your speed math skills must be backed by a strong exam strategy.

  • Round to Estimate: Don't try to solve a problem with exact decimals if the options are far apart.
  • Look for Clues: Check the unit digit of the options. This can sometimes eliminate wrong answers instantly. For example, if a calculation ends in $3 \times 7 = 21$, the unit digit of the answer must be 1.
  • Practice with Timers: Train your mind to work under pressure. Use online practice games and mock tests to simulate exam conditions.

6. The Key to Success: Consistent Practice

Speed math is a skill, not a trick. It requires regular practice to become second nature. Dedicate 15-20 minutes every day to mental math drills. The more you practice, the more these techniques will become intuitive, helping you solve problems faster and more accurately in the final exam.

Ready to get on track for your exam?

Test your speed with our Timed Challenge and build your calculation speed!