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The figure below shows a shaded circular region inside a larger circle:




What is the probability that a point chosen inside the larger circle is not in the shaded region?



A. 84%
B.50%
C.42%
D.16%

Answer 1

The formula for a circle is pi*r^2
The area of the larger circle is pi*5^2=25pi
The area of the smaller circle is pi*2^2=4pi
Thus the chance that the point will be picked inside the smaller circle is 4pi/25pi or 4/15 or 16%
Thus the chance that it's not in the shaded region is 84%