Your mom has sent you to buy a new suit and will let you get new shoes too if you keep it under $200. The suit you want to buy i
2 answers:
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It the wiper blade (and arm) made a full rotation, 2 circles would be formed.
One small circle with radius b, and a larger circle with radius a+b.
The areas of these 2 circles are respectively:
and
120° is 1/3 of a complete angle 360° which form a circle, so the areas formed by the arm of length b, and the arm + the wiper blade (a+b) are:
and 
in squared respectively.
the actual wiped area is
(in squared)
Area of the window is 54*24= 1296 (in squared)
thus, the ratio of the wiped area to the whole area of the window is 351.7/1296=0.271
Converted to percentages, this is 27.1%
Answer: 27.1%
One small circle with radius b, and a larger circle with radius a+b.
The areas of these 2 circles are respectively:
120° is 1/3 of a complete angle 360° which form a circle, so the areas formed by the arm of length b, and the arm + the wiper blade (a+b) are:
the actual wiped area is
Area of the window is 54*24= 1296 (in squared)
thus, the ratio of the wiped area to the whole area of the window is 351.7/1296=0.271
Converted to percentages, this is 27.1%
Answer: 27.1%
I suspect 4/2 should actually be 4/3, since 4/2 = 2, while 4/3 would make V the volume of a sphere with radius r. But I'll stick with what's given:
In Mathematica, you can check this result via
D[4/2*Pi*r^3, r]