Answer :

First convert feet into in.
4ft = 48in
6ft = 72in
Then add up the 4 sides of the rectangle
(2 sides are 48 in long and the other two are 72 in long)
48in +48in+72in+72in = 240in
The perimeter of the rectangle is 240in
P = 2(4ft + 6ft)(12 in/ft) = 2(4+6)(12) = 2(10)(12) = 24(10) = 240 inches