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• Nov 19th 2012, 09:07 PM
MarkFL
No, you need to divide by $12^3$...essentially a 12 for each of the 3 spatial dimensions.

$7128\text{ in}^3\cdot\left(\frac{1\text{ ft}}{12\text{ in}} \right)^3=\frac{7128}{12^3}\,\text{ft}^3=156.75 \text{ ft}^3$
• Nov 19th 2012, 09:14 PM
ophischauss
Oh, ok that makes since. So for part 5 would I use the formula 1/2*b*h so 1/2*(99)*(104) = 5148 in^2
• Nov 19th 2012, 09:22 PM
MarkFL
No, you have a trapezoid, not a triangle. You want to use:

$A=\frac{h}{2}(B+b)$

where:

$h=99$

$B=104$

$b=32$
• Nov 19th 2012, 09:27 PM
ophischauss
O.k., sorry for not getting this right away, thanks for your patience lol.
So the answer would then be 6732
• Nov 19th 2012, 09:48 PM
MarkFL
An impatient person has no business trying to help on a forum. You are doing fine.

Yes, that is the correct answer. Now, in order to find this area using integration, I recommend orienting your coordinate axes such that the origin is at the bottom corner under the lowest point of the ceiling. We will then want to write the upper slanting edge of the wall as a linear function. What would the y-intercept and the slope be?
• Nov 19th 2012, 09:54 PM
ophischauss
Would the slope be 8 and the y-intercept 32?
• Nov 19th 2012, 09:58 PM
MarkFL
You have the correct intercept, but for the slope, think of the rise over run of an individual step.
• Nov 19th 2012, 10:00 PM
ophischauss
ok so the slope would be 8/11?
• Nov 19th 2012, 10:18 PM
MarkFL
Yes, good work! So, what would the linear function representing the slanted edge be?
• Nov 19th 2012, 10:20 PM
ophischauss
(8/11)x+32?
• Nov 19th 2012, 10:26 PM
MarkFL
Exactly! Now, over what interval do you want to integrate?
• Nov 19th 2012, 10:27 PM
ophischauss
Would it be from 5 to 13?
• Nov 19th 2012, 10:35 PM
ophischauss