The radii of three concentric circles are 2cm, 3cm and 4cm

Find the ratio of the shaded areas A (the second circle from the inside) and B(the outer circle)
(Hint: don't substitute for pi)

3 answers

I assume
A is the area between the 2-cm and the 3-cm circles
B is the area between the 3-cm and 4-cm circles.

A = pi(3^2 - 2^2) = 5pi
B = pi(4^2 - 3^2) = 7pi

B/A = 7/5

4:9

7:88

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