AQA · Mathematics · 8300
GCSE Maths: Area: circles
Geometry & Measures · AQA GCSE Maths (8300). Cards are generated from the Corbettmaths textbook exercise and practice questions for Area: circles (Corbettmaths Video 40), and every card links back to the exact page it came from. Practice tests are drawn from this deck’s own cards. Source material © Corbettmaths — used with attribution.
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The formula for the area of a circle is ?
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πr²
What must you do to the diameter to find the radius of a circle?
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Divide the diameter by 2 (or multiply by 0.5).
If a circle's area is given as 49π cm², what is its radius?
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7 cm. Since A = πr², we have πr² = 49π, so r² = 49, giving r = 7.
How do you find the area of a semicircle with radius r?
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Use the formula (πr²)/2 or πr²/2, which is half the area of a full circle.
If a circle and a square touch at four points with the circle inside, what is the relationship between the circle's diameter and the square's side length?
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The circle's diameter equals the square's side length.
If the circumference of a circle is C, what formula gives its area?
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A = C²/(4π). First find r from C = 2πr (so r = C/(2π)), then use A = πr².
To find the radius of a circle when its area A is known, what formula do you use?
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r = √(A/π). Rearrange A = πr² to solve for r.
What does it mean to give an answer 'in terms of π'?
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Leave π as a symbol in the answer rather than using a numerical approximation (e.g., 25π cm² instead of 78.5 cm²).
If circle B has an area 4 times larger than circle A, what is the ratio of their radii?
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The ratio is 1:2. Since area scales with r², if area increases by factor 4, radius increases by √4 = 2.
How do you calculate a shaded region between two circles?
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Calculate the area of the larger circle, subtract the area of the smaller circle.
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