Equation of a circle
Edexcel GCSE Maths revision on Equation of a circle. Aligned to the Pearson Edexcel GCSE Mathematics 1MA1 specification. This bank has 17 practice questions on this topic.
Sample questions (3 of 17)
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Question 1
What is the equation of a circle with a centre at the origin and a radius of 5?
- A) x^2 + y^2 = 25
- B) x^2 + y^2 = 10
- C) x + y = 25 units
- D) x + y = 5 units
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Answer: x^2 + y^2 = 25
The correct answer is x^2 + y^2 = 25 because the radius is squared in the circle equation (5 squared is 25). Students often incorrectly select 10 because they double the radius instead of squaring it.
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Question 2
What is the radius of the circle defined by the equation x^2 + y^2 = 49?
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Answer: 7
The radius is the square root of 49, which is 7. The equation x^2 + y^2 = r^2 identifies the radius by taking the square root of the constant term.
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Question 3
Which of these points lies on the circumference of the circle given by x^2 + y^2 = 169?
- A) Point (5, 12)
- B) Point (7, 10)
- C) Point (3, 13)
- D) Point (9, 11)
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Answer: Point (5, 12)
The point (5, 12) lies on the circle because 5 squared plus 12 squared equals 25 plus 144, which is 169. Other options fail the calculation when tested against the radius squared.
Want to test yourself on the remaining cards for this topic?
14 more questions on Equation of a circle — plus mistakes tracking and spaced repetition across the whole Maths spec.