Topic Details (Notes format)

How to Calculate the Area of a Circle

Subject: Mathematics

Book: Maths Mastery

The area of a circle is given by the formula A = πr², where r is the radius—the distance from the center to the circumference. If you have a circle with radius 5 cm, its area is π × 5² = 25π cm². In practical terms, you might need to measure the space a circular rug covers or the cross-sectional area of a circular pipe. Knowing how to apply A = πr² is foundational in geometry, engineering, and architecture. Pairing this knowledge with circumference or volume formulas further expands your capability to handle circular shapes in diverse projects and daily scenarios.

Practice Questions

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

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If a rectangle has a length of 10 cm and a width of 6 cm, what is its perimeter?

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A train 150 m long passes a pole in 15 seconds. What is its speed?

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What is the value of x if 3x + 7 = 16?

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A number is increased by 20% and then decreased by 10%. What is the net change?

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What is the LCM of 15 and 20?

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If x - y = 5 and x + y = 15, what is the value of x?

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

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What is the square root of 121?

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If the angles of a triangle are in the ratio 2:3:4, what is the measure of the largest angle?

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