Answer:
Option F, 10 inches.
Explanation:
For a circle of radius R, the perimeter is:
P = 2*pi*R
such that pi = 3.14
If we have a section of that circle defined by an angle θ, the length of the arc is:
A = (θ/360°)*P = (θ/360°)* 2*pi*R
In this case, we have a circle whose radius is defined by the length of the windshield wiper.
We also know that in one 90° revolution (so it travels the length of the arc of 90° two times) the tip travels a distance of 31 in.
Then:
A = 2*[(90°/360°)*2*3.14*R] = 31in
We need to solve this for R.
R = 31in/( 2*(90°/360°)*2*3.14) = 9.8in
We can round this to the next whole number:
R = 10in
The correct option is F.