ACT · Coordinate Geometry · Introduction to conics
Question act-q-00438
Medium Multiple choice No calculator
The question
A circle has radius 4. What is its area, in terms of π?
- 4π
- 16π
- 32π
- 8π
Show answer & worked solution
Answer: 16π
Worked solution. Area of a circle is πr². Here r = 4, so area = π × 4² = 16π.
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.