Questions
3–5 questions
Difficulty
Easy
Importance
High scoring potential
Overview
Quantitative Arithmetic forms the foundation of the numerical ability section in PSU recruitment exams, testing your speed and accuracy in basic calculations. It covers essential topics like percentages, ratios, and averages which are prerequisites for more complex data interpretation questions. Mastering these builds the mental agility required to solve time-bound competitive papers efficiently.
Percentages and Fractions
Percentage calculations are the building blocks for profit and loss, simple interest, and compound interest problems. Being able to quickly convert fractions to percentages and vice versa saves critical seconds during the exam.
- Fraction to percentage conversion table (e.g., 1/8 = 12.5%)
- Base value identification in percentage increase/decrease
- Successive percentage change formula: a+b+(ab/100)
- Application in tax, commission, and population growth problems
Ratio and Proportion
Ratio-based methods often provide faster solutions than algebraic equations for problems involving mixtures and ages. Understanding how to handle constant ratios is key to simplifying complex distribution tasks.
- Dividing a quantity in the ratio a:b
- Mean proportional calculation: square root of ab
- Concept of combined ratios (A:B and B:C to A:B:C)
- Direct vs. inverse proportion behavior
Averages and Weighted Means
Averages are frequently tested through topics like speed, marks, and income distributions. The weighted average approach is particularly useful for finding composite values when the quantities differ.
- Arithmetic Mean: Sum of observations / Number of observations
- Change in average when a value is added or replaced
- Calculation of weighted average
- Properties of the median in grouped data sets
Formula Sheet
Percentage change = (Difference / Original Value) * 100
Sum of first n natural numbers = n(n+1)/2
Weighted Average = (w1x1 + w2x2) / (w1 + w2)
Exam Tip
Prioritize speed by memorizing common fraction-to-percentage conversions up to 1/20, as this is the single most effective way to gain an edge in arithmetic sections.
Common Mistakes
- Mistaking the base value when calculating percentage increases or decreases.
- Attempting to solve ratio problems using long algebraic equations instead of the unitary method.
- Forgetting to account for the change in the total number of items when replacing values in an average calculation.
More Revision Notes
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