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

The perimeter of a rectangle is 40 cm, and its length is 12 cm. What is its width?

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A train 120 meters long is moving at a speed of 54 km/h. How long will it take to pass a pole?

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A cone has a base radius of 7 cm and height of 24 cm. What is its volume?

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If the sides of a triangle are 6 cm, 8 cm, and 10 cm, what is the area of the triangle?

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If x^2 + 4x + 4 = 0, what is the value of x?

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If a:b = 5:7 and b:c = 6:11, what is a:c?

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If a right triangle has legs of 9 cm and 12 cm, what is the length of the hypotenuse?

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If a:b = 3:4 and b:c = 5:6, what is a:c?

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If the sum of three consecutive integers is 72, what are the integers?

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A rectangle has a length of 10 cm and a width of 5 cm. What is the diagonal of the rectangle?

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