A circle has radius 3 cm and a second circle has radius 4 cm. By what factor is the area of the second circle larger than the first?
Answer and explanation
Correct answer: B. 16/9
- Step 1: Area is proportional to the radius squared.
- Step 2: Factor = (4/3) squared = 16/9.
Answer
16/9.
Why not the others: 4/3: areas depend on the square of the radius, not the radius itself. 7: the areas were subtracted without dividing. 64/27: the cube of the radius was used.
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