Precalc Trig Arc Length Question

[A123]

Homework Statement

http://education.Alberta.ca/media/9451970/07_math30-1_released_2014-15.pdf
question #7

Homework Equations

a=theta*r

The Attempt at a Solution

I did a=(5pi/6)*20 but the answer is not A

 

[SteamKing]

Homework Statement

http://education.Alberta.ca/media/9451970/07_math30-1_released_2014-15.pdf
question #7

Homework Equations

a=theta*r

The Attempt at a Solution

I did a=(5pi/6)*20 but the answer is not A

I think 'total perimeter' here means you go entirely around the area which is swept out by the wiper.

 

[Mark44]

I think 'total perimeter' here means you go entirely around the area which is swept out by the wiper.

I agree with SteamKing's appraisal.

 

[A123]

I think 'total perimeter' here means you go entirely around the area which is swept out by the wiper.

Yeah I just went back to it and I missed that word completely lol.
Its [(5pi/6)*20] + 16(2) + [(5pi/6)*4]
I was too focused on what's inside