The formula for combinations is
C=n!/[(n-r)!*r!]
where
n is the total number of objects you choose from
r is the number that you choose to arrange
in this problem
n=4 aluminum side panels measures
r=2 aluminum side panels measures
C=4!/[(4-2)!*2!]----->
C=4!/[2!*2!]---> (4*3*2!)/(2!*2*1)
C=6
1) 8 ft x 10 ft
2) 8 ft x 12 ft
3)8 ft x 15 ft
4) 10 ft x 12 ft
5) 10ft x 15 ft
6) 12 ft x 15 ft
additionally, we have each measure with itself
7) 8 ft x 8 ft
8) 10 ft x 10 ft
9) 12 ft x 12 ft
10) 15 ftx 15 ft
the answer is
10 possible sets
