Homework Help: geometry

Posted by mary on Monday, April 18, 2011 at 9:34am.

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!

geometry - Jai, Monday, April 18, 2011 at 9:54am
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~ :)
geometry - mary, Monday, April 18, 2011 at 10:05am
Thank you so much Jai-that really cleared thing up

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