A circle has radius 2 cm and a second circle has radius 5 cm. By what factor is the area of the second circle larger than the first?
Answer and explanation
Correct answer: A. 25/4
- Step 1: Area is proportional to the radius squared.
- Step 2: Factor = (5/2) squared = 25/4.
Answer
25/4.
Why not the others: 5/2: areas depend on the square of the radius, not the radius itself. 21: the areas were subtracted without dividing. 125/8: the cube of the radius was used.
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