Railways Notes / Mathematics (Quantitative Aptitude) / Chapter 6
Chapter 6 of 31

Percentage

The fraction-equivalent method for fast percentage calculation, plus successive percentage change — used across Profit/Loss, SI/CI, and DI.

📖 ~4 min read 📐 RRB NTPC / Group D — Mathematics

Percentage Basics

Percentage means "per hundred." Percentage = (Value / Total) × 100

Percentage-to-Fraction Table

%Fraction%Fraction
50%1/216.67%1/6
33.33%1/314.28%1/7
25%1/412.5%1/8
20%1/511.11%1/9
10%1/106.25%1/16

Successive Percentage Change

Net % change = a + b + (a×b)/100 — use negative signs for decreases

More Than / Less Than Trap

⚠️ If A is x% more than B, B is NOT x% less than A. Correct formula: B is [x/(100+x)]×100% less than A.
  • To increase a number by x%: multiply by (100+x)/100
  • To decrease a number by x%: multiply by (100−x)/100

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