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Board Exam Notes

Arithmetic Notes

Questions

6–8 questions per paper

Difficulty

Medium

Importance

High yield for SSC and IBPS/SBI

Overview

Arithmetic forms the backbone of quantitative aptitude in SSC and banking exams, testing your ability to process numerical data under strict time constraints. Mastery of these concepts is essential as they serve as the foundation for Data Interpretation and advanced topics, making speed and mental calculation the ultimate keys to success.

Percentages and Averages

Percentage is the universal language of arithmetic, while Averages help in understanding central tendencies quickly. Developing the ability to convert fractions to percentages mentally is a prerequisite for solving complex arithmetic problems efficiently.

  • Fraction to %: 1/8=12.5%, 1/6=16.66%, 1/9=11.11%
  • Percentage Change: (New-Old)/Old * 100
  • Weighted Average Formula: (n1*a1 + n2*a2) / (n1+n2)
  • Successive change formula: x + y + (xy/100)

Profit and Loss

This topic relies on understanding the relationship between Cost Price, Selling Price, and Marked Price. Exam questions often involve successive discounts and discrepancies in weights, requiring a clear grasp of the base value.

  • Profit % = (Profit/CP) * 100
  • Loss % = (Loss/CP) * 100
  • Discount % = (Discount/MP) * 100
  • Effective CP = MP * (100-D1)/100 * (100-D2)/100

Simple and Compound Interest

Interest calculation is a staple in banking exams. While Simple Interest follows a linear growth pattern, Compound Interest grows exponentially, and mastering the shortcut for 2-year and 3-year cycles is crucial for saving time.

  • SI = (P*R*T)/100
  • CI = P(1+R/100)^n - P
  • CI-SI for 2 years: P * (R/100)^2
  • Effective annual rate for 2 yrs: 2R + R^2/100

Ratio and Proportion

Ratio techniques allow you to bypass heavy algebraic equations by comparing quantities directly. This is the fastest method to solve problems involving mixture, partnership, and age distribution.

  • Cross-multiplication method for ratio changes
  • Mean proportional of a and b: sqrt(ab)
  • Third proportional of a and b: b^2/a
  • Componendo and Dividendo rule

Formula Sheet

Profit = SP - CP

SI = (P*R*T)/100

CI = P(1+R/100)^T - P

A = P(1 + R/100)^T

Exam Tip

Memorize the fraction-to-percentage table up to 1/20 to solve 30% of your quantitative paper mentally without touching a pen.

Common Mistakes

  • Mistaking Base Value: Calculating percentage increase or profit on Selling Price instead of Cost Price.
  • Ignoring Units: Failing to normalize units (e.g., mixing months and years) in interest calculations.
  • Over-reliance on Algebra: Using long-form equations instead of ratio-based shortcuts, leading to time exhaustion.

More Revision Notes

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