geometry
posted by mary on .
Find the surface area of a rectangular prism with a length of 8 inches, a width of 5 inches and a height of 2 inches.
so far this is what I have
(2(8)+2(5))2=72 + 2(8.5)=80
my answer is 152in^2
the books answer is 132in^2
What did I do wrong???? Thanks for the help!

recall that surface area of rectangular prism is given by
SA = 2*(LW + LH + WH)
where
L = length
W = width
H = height
substituting,
SA = 2*[(8)(5) + (8)(2) + (5)(2)]
SA = 2*(40 + 16 + 10)
SA = 2*(66)
SA = 132 in^2
hope this helps~ :) 
Thank you so much Jaithat really cleared thing up