Answer: 0.07 (choice B)
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Explanation:
Let's define two events: B = hitting bullseye, and, T = hitting the third (outermost) ring
To figure out the probabilities of each event happening, we need to find the areas of each region. The bullseye is a circle with radius 6 inches (half of diameter 12), so the area is roughly...
A = pi*r^2 = pi*6^2 = 36pi
The radius of the outermost circle is 6+5+5 = 16 inches, leading to an area of
A = pi*r^2 = pi*16^2 = 256pi
So P(B) = (36pi)/(256pi) = 9/64 is the probability of hitting bullseye
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The area of the third ring is equal to the difference of the overall largest circle and the second largest circle.
The second largest circle has a radius of 6+5 = 11 inches with area pi*11^2 = 121pi square inches
So the third ring has an area of 256pi - 121pi = 135pi square inches
P(T) = probability of hitting the third ring
P(T) = (135pi)/(256pi)
P(T) = 135/256
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The last thing to do is to multiply the two probabilities P(B) and P(T). This works because the two events B and T are independent
P(B and T) = P(B)*P(T)
P(B and T) = (9/64)*(135/256)
P(B and T) = 0.07415771484376
P(B and T) = 0.07
