SOLUTION: Okay, so I'm really struggling on this question, and I was wondering if someone could tell me what I'm doing wrong. Ralph is painting the barn below, including the sides and roo

Algebra ->  Surface-area -> SOLUTION: Okay, so I'm really struggling on this question, and I was wondering if someone could tell me what I'm doing wrong. Ralph is painting the barn below, including the sides and roo      Log On


   

Question 1181041: Okay, so I'm really struggling on this question, and I was wondering if someone could tell me what I'm doing wrong.
Ralph is painting the barn below, including the sides and roof. He wants to know how much paint to purchase.
The picture is in the link below:
https://founders.edtell.com/access/content/group/edtell_content_geometry/General%20Prisms.png

a. What is the total surface area that he is going to be painting? Round your answer to the nearest hundredth.
b. If one paint can covers 57 square feet, how many paint cans should he purchase?
c. If each paint can costs $23.50, how much will the paint cost?
d. Once the barn is finished being painted, there is going to be a party. Ralph wants to know how many people to invite to the party. What is the volume of the inside of the barn?

Here is the work I've done. I was told that it's incorrect. I looked back over it a couple of times, but I couldn't figure out where I went wrong. Can somebody please help me?
A.)
45x15x2=1350
20x15x2= 600
40x45x2= 3600
20x4= 80
1350+600+3600+80= 5630 ft
B.)
5630/57=98.77
98.77~99 cans
C.)
99x23.5=2326.5
2326.5= $2,326.50
D.)
45x20x15=19575
(1/2)x80x40x4=6400
19575+6400=25975 ft^3
Found 2 solutions by MathLover1, ikleyn:
Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!

PART A
The barn is constructed by the following 2D shapes
Two triangles of height = 4 and base = 20
Area = 2 * (1/2)*4*20) = 80}}}
Two rectangles of length = 20 and width = 15
Area+=+2+%2A+20+%2A+15+=+600
Two rectangles of length = 45 and width =+15
Area+=+2+%2A+45%2A15+=+1350
One base of length = 45 and width = 15
Area+=+45+%2A15+=+675
Two rectangles on each on one side of the roof. We have the length = 45 but not the width. We can work out the width by using Pythagoras theorem
w%5E2+=+4%5E2+%2B+10%5E2
w%5E2=+16+%2B+100
w%5E2=+116
w+=+sqrt%28116%29+=+10.77
Area of the two rectangles on the roof part is = 2%2A10.77%2A+45+=+969.33
Total area to paint = 969.33%2B675%2B1350%2B600%2B80+=+3674.33(to the nearest hundreth) ≈ 3700

PART C
one paint can covers 57 square feet
3700%2F57=65->need 65 cans of paint
Total cost of paint =+65+%2A23.50+=+1527.50
PART D
The barn is constructed by a cuboid and a rectangular prism
Volume of cuboid V=+length+%2Awidth+%2A+height
V=+20%2A45%2A15
V=13500
V of triangular prism = Area of cross section × depth
V+=+%28%281%2F2%29%2A4%2A20%29+%2A+45
V+=+1800
Total volume
= 1800+%2B+13500+=+15300

Answer by ikleyn(52784) About Me  (Show Source):
You can put this solution on YOUR website!
.

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