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

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The sides of a triangle are 13 cm, 14 cm, and 15 cm. What is its area?

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If a cylinder has a radius of 7 cm and height of 10 cm, what is its volume?

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If the radius of a circle is 7 cm, what is its circumference?

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If x:y = 4:5 and y:z = 2:3, what is x:z?

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The area of an equilateral triangle with side length 6 cm is:

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If x + y = 10 and xy = 21, what is the value of x³ + y³?

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

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If x^2 - 6x + 9 = 0, what is the value of x?

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What is the area of a sector of a circle with radius 14 cm and central angle 90°?

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