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If the length of the radius of the circle is doubled, how does that affect the circumference and area. Explain please.

User Aobs
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radius - r
area:

A_1=\pi r^2
circumference:

C_1=2 \pi r

the length of the radius is doubled
radius - 2r
area:

A_2=\pi * (2r)^2=\pi * 4r^2=4 \pi r^2
circumference:

C_2=2 \pi * 2r=4 \pi r


(A_2)/(A_1)=(4 \pi r^2)/(\pi r^2)=4 \\ \\ (C_2)/(C_1)=(4 \pi r)/(2 \pi r)=(4)/(2)=2

When the length of the radius is doubled, the area is quadrupled and the circumference is doubled.
User Petrashka Siarhei
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