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Picture is not drawn to scale.

The dimensions of circle B are twice the dimensions of circle A. The area of circle Bis 64$src=https://media.studyisland.com/cgi-bin/mimetex.cgi?\pi$ cm2.

What is the area of circle A?

Guest Feb 25, 2015

#2
+94105
+5

the radii are in the ratio 1:2

so the area has to be in the ratio     $$1^2:2^2\quad=\quad 1:4$$

the big one's area is 64pi

so the little ones area is          $$64\pi/4 = 16\pi \quad cm^2$$

Melody  Feb 26, 2015
#1
+92674
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If the area of circle B = 64*pi cm^2, it's radius must be 8 cm.

Then, the radius of circle A must be 1/2 of that = 4cm

And it's area = pi*(4cm)^2  = 16pi cm^2

CPhill  Feb 26, 2015
#2
+94105
+5

the radii are in the ratio 1:2

so the area has to be in the ratio     $$1^2:2^2\quad=\quad 1:4$$

the big one's area is 64pi

so the little ones area is          $$64\pi/4 = 16\pi \quad cm^2$$

Melody  Feb 26, 2015