Summary of Aptitude Made Easy – Problems on Percentages full series, Learn maths #StayHome

Main Ideas and Concepts

• Understanding Percentages

  Percentages represent a part of a whole expressed in terms of 100. The numerator in a percentage calculation is referred to as the "rate percent."

• Basic Calculations

  To find a percentage of a number, divide the numerator by the denominator (100) and multiply by the number in question. Example: To find what percent 3 is of 60, use the formula: (3/60) * 100 = 5%.

• Conversion Between Percentages and Fractions

  To convert a percentage to a fraction, divide by 100. To convert a fraction to a percentage, multiply by 100. Example: 20% = 20/100 = 1/5; 1/5 = 20%.

• Memorization of Key Fractions

  Memorize the values of fractions from 1/1 to 1/10 and their corresponding percentages for quick calculations. Example: 1/3 = 33.33%, 1/4 = 25%, etc.

• Common Percentage Problems
  • Finding Percentages: X is what percent of Y is calculated as (X/Y) * 100.
  • Increasing/Decreasing Values by a Percentage:
    • For an increase of X%, the new value = (1 + X/100) * original value.
    • For a decrease of X%, the new value = (1 - X/100) * original value.
• Salary Problems

  Understanding how to calculate the percentage difference between salaries. Example: If Kanish's salary is 20% more than Ashok's, calculate how much less Ashok's salary is compared to Kanish's.

• Expenditure Problems

  The relationship between rate, consumption, and expenditure is crucial. If the rate increases, the consumption must decrease to keep expenditure constant. Example: If the rate increases by 50%, the consumption must decrease by 33.33% to maintain the same expenditure.

• Formula for Combined Percentage Changes

  When two values are increased by percentages A and B, the overall change can be calculated using the formula: A + B + (AB/100).

Methodology and Instructions

• Convert Percentages to Fractions: Divide the percentage by 100.
• Convert Fractions to Percentages: Multiply the fraction by 100.
• Calculate Percentage of a Number: Use the formula (X/Y) * 100.
• Find New Values After Increase/Decrease:
  • Increase: New Value = Original Value * (1 + X/100)
  • Decrease: New Value = Original Value * (1 - X/100)
• Salary Comparisons: Set a base value (e.g., 100) for easier calculations.
• Expenditure and Consumption: Use the formula: Expenditure = Rate * Consumption.

Featured Speakers/Sources

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