90
one revolution is the circumference of the circle.
C=
d=90
13-9 = 4ft
4/2 = 2ft
2^2+4^2=20
Length of the sides: √20 or 4.47ft
13+9+4.47+4.47 = 30.94ft
The answer is C
We want to choose 4 people and we have 6 people to choose from. This is a combination of 6, 4 by 4. Also called <em>six choose four</em>.
The following formula:

Is the combination of
objects choosen from a total of
. It's
choose
.
For our problem, we just need to compute the following:

Thus

Therefore the answer is 15 different combinations