Summary of "Percentage - Shortcuts & Tricks for Placement Tests, Job Interviews & Exams"
Summary of the Video: "Percentage - Shortcuts & Tricks for Placement Tests, Job Interviews & Exams"
Main Ideas and Concepts
- Basic Definition of Percentage
- Percentage means a part of a whole.
- Symbol (%) means divide by 100.
- Example: 25% = 25 ÷ 100 = 0.25.
- Whole or entire thing = 100%.
- Common Percentage-Fraction Equivalents
- 1/2 = 50%
- 1/3 ≈ 33.33%
- 1/4 = 25%
- 1/5 = 20%
- 1/8 = 12.5%
- Multiples like 3/4 = 75%, etc.
- Useful for quick conversions in problems.
- Basic Percentage Calculations
- Percentage of a number = (Percentage ÷ 100) × Number.
- Shortcut for 10%, 1%, etc.: Move decimal point to the left.
- Example: 10% of 260 = 26 (decimal moved one place).
- 1% of 693 = 6.93 (decimal moved two places).
- For other percentages, break down:
- Example: 39% of 260 = 40% of 260 - 1% of 260 = 104 - 2.6 = 101.4.
- Similarly, 63% = 60% + 3%.
- Finding Unknown Quantities in Percentage Problems
- When given Percentage of a quantity equals a number, solve for the unknown.
- When asked what percent one quantity is of another, use:
Percentage = (Part / Whole) × 100 - When comparing two quantities with percentages, use cross multiplication.
- Percentage Increase and Decrease
- To find Percentage more/less than another quantity, use:
(Difference / Reference Quantity) × 100 - Example: If rice price is 30% less than wheat, wheat price is 42.85% more than rice.
- To find Percentage more/less than another quantity, use:
- Successive Percentage Changes
- Increase then decrease by the same Percentage does not bring back the original value.
- Example: Increase by 10% then decrease by 10% results in a net 1% decrease.
- Practical Word Problems & Techniques
- Use assumed values (usually 100) to simplify calculations.
- For consumption/expenditure problems, equate expenditures before and after price changes.
- Use Venn diagram logic for overlapping percentages (e.g., students failing in two subjects).
- For Election problems, total votes are split according to Percentage votes received.
- For literacy or Population problems, assume total population and calculate parts accordingly.
- General Tips
- Percentage is always multiplication by (Percentage ÷ 100).
- When finding Percentage of quantity 1 in relation to quantity 2, divide and multiply by 100.
- For Percentage increase/decrease, calculate difference relative to the reference quantity.
- Use decimal point shifting for quick calculation of 1%, 10%, etc.
- Break complex percentages into sums/differences of simpler percentages (e.g., 39% = 40% - 1%).
Detailed Methodologies / Instructions
- Calculating Percentage of a Number:
- Multiply the number by (Percentage ÷ 100).
- Shortcut: For 10%, move decimal one place left; for 1%, move two places left.
- For other percentages, break down into sums/differences of 10%, 1%, etc.
- Finding Percentage When Two Quantities Are Given:
Percent = (Quantity 1 / Quantity 2) × 100Useful to find what percent one quantity is of another. - Solving for Unknown Quantity in Percentage Equation:
When given
x%ofy = z, solve:y = (z × 100) / x - Percentage Increase / Decrease:
To find how much percent one quantity is more/less than another:
Percent change = (Difference / Reference quantity) × 100Reference quantity is the quantity to which comparison is made. - Successive Percentage Changes:
- Calculate each step based on the new amount.
- Example: Increase by 10% then decrease by 10%:
Category
Educational
