ACT · Coordinate Geometry · Introduction to conics
Question act-q-00443
Medium Multiple choice No calculator
The question
A circle has radius 5. What is its area, in terms of π?
- 5π
- 10π
- 50π
- 25π
Show answer & worked solution
Answer: 25π
Worked solution. Area of a circle is πr². Here r = 5, so area = π × 5² = 25π.
Why each wrong choice is wrong. Confusing area (πr²) with circumference (2πr) is the dominant error here. The 2πr distractor catches it perfectly.
Test-day tactic. Area scales as the square of the radius; circumference scales linearly. When in doubt, sketch a unit circle and check.
About this question type
A small number of items ask you to recognize a conic section from its equation. Parabolas have a single squared variable; ellipses and hyperbolas have both x² and y² with the same sign (ellipse) or opposite signs (hyperbola).
You will see a question shaped like this one on roughly every other official ACT form, typically at a moderate position in the section — solidly within the range that separates a 600-band student from a 700-band student. Treat any miss in this subtopic as a signal to drill the subtopic page before you do another full practice test.