Question 552709: My question is on the surface area of a rectangular prism, i am givin the surface area of 242.2 square inches. The width of the rectangle is 6.4in and the lenght is 4.7in. I have to find the height. This question is for a St.Jude Children's Research Hospital found raiser, so this is very important to me that i get it answered.
I have to find the missing length, the height.
Surface area = 242.2 square inches
Width = 6.4 in
lenth = 4.7 in
Height = needs found
thank you in advance
Found 2 solutions by Earlsdon, letsgetthistraight:
Answer by Earlsdon(6294)   (Show Source):
You can put this solution on YOUR website! The suface area (SA) of a rectangular prism of length (L), width (W) and height (h) can be expressed by:
SA = 2(L*W)+2(L*h)+2(W*h) This is just adding the areas of the 3 identical pairs of the six faces of the prism.
SA is given as 242.2 sq.in.
Substitute the given values: SA = 242.2, L = 4.7, and W = 6.4
242.2 = 2(4.7*6.4)+2(4.7h)+2(6.4h) Divide by 2 to simplify a bit.
121.1 = (4.7*6.4)+4.7h+6.4h
121.1 = 30.8+11.1h Subtract 30.8 from both sides.
90.3 = 11.1h Divide both sides by 11.1
h = 8.13515 inches.
Answer by letsgetthistraight(1)  (Show Source):
You can put this solution on YOUR website! You can use the formula: 
242.2 = 2(HxL) + 2(LxW) + 2(WxH) Now that you have it written out, fill it in:
242.2 = 2(Hx4.7) + 2(4.7x6.4) + 2(6.4xH) Solve what you can, and divide by 2:
121.1 = 4.7H + (4.7x6.4) + 6.4H
121.1 = 4.7H + 30.08 + 6.4H
121.1 = 11.1H + 30.08 Next, subtract 30.08 from each side:
91.02 = 11.1H
H = 8.2
I have the booklet myself and have done the question, and in the back of the booklet the answers are shown. I'm supposed to show the work, so I did this and checked the answer: 8.2
I was correct.
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