Topic Details (Notes format)

How to Calculate the Percentage of a Number?

Subject: Mathematics

Book: Maths Mastery

Percentages are central to countless real-world applications—from calculating exam marks to determining discounts and interest rates. The general formula to find a percentage is: (Part / Whole) × 100%. However, if you already know the rate and the whole, use Percentage of a Number = (Rate ÷ 100) × Whole. For example, to calculate 20% of 150, convert 20% to 0.20, then multiply: 0.20 × 150 = 30. This concept is pivotal in areas like finance and data analysis, so practice by computing percentages for tips in restaurants, taxes on shopping bills, or proportionate contributions in group projects. Mastering this skill builds a strong foundation for advanced percentage operations such as percentage increase, decrease, and compound interest calculations.

Practice Questions

If x^2 - 5x + 6 = 0, what are the roots?

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If the length of a rectangle is doubled and the width is halved, what is the change in area?

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If x = 3 and y = 4, what is the value of x^2 + y^2?

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The sum of the reciprocals of two numbers is 1/4. If one number is 12, what is the other?

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If a + b = 10 and ab = 21, what is the value of a^2 + b^2?

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A car covers a distance of 150 km in 2.5 hours. What is its average speed?

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If x² - 9x + 18 = 0, what are the roots of the equation?

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If sin(x) = 3/5 and x is in the first quadrant, what is cos(x)?

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