# Math Help - Calc Word Problem. Please Help!!!

1. ## Re: Calc Word Problem. Please Help!!!

No, you need to divide by $12^3$...essentially a 12 for each of the 3 spatial dimensions.

$7128\text{ in}^3\cdot\left(\frac{1\text{ ft}}{12\text{ in}} \right)^3=\frac{7128}{12^3}\,\text{ft}^3=156.75 \text{ ft}^3$

2. ## Re: Calc Word Problem. Please Help!!!

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

3. ## Re: Calc Word Problem. Please Help!!!

No, you have a trapezoid, not a triangle. You want to use:

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

where:

$h=99$

$B=104$

$b=32$

4. ## Re: Calc Word Problem. Please Help!!!

O.k., sorry for not getting this right away, thanks for your patience lol.
So the answer would then be 6732

5. ## Re: Calc Word Problem. Please Help!!!

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?

6. ## Re: Calc Word Problem. Please Help!!!

Thank-you, I appreciate your help.
Would the slope be 8 and the y-intercept 32?

7. ## Re: Calc Word Problem. Please Help!!!

You have the correct intercept, but for the slope, think of the rise over run of an individual step.

8. ## Re: Calc Word Problem. Please Help!!!

ok so the slope would be 8/11?

9. ## Re: Calc Word Problem. Please Help!!!

Yes, good work! So, what would the linear function representing the slanted edge be?

(8/11)x+32?

11. ## Re: Calc Word Problem. Please Help!!!

Exactly! Now, over what interval do you want to integrate?

12. ## Re: Calc Word Problem. Please Help!!!

Would it be from 5 to 13?

13. ## Re: Calc Word Problem. Please Help!!!

and if that is the interval would it be:
(4/11)x^2+32x evaluated from 5 to 13= 308.364

14. ## Re: Calc Word Problem. Please Help!!!

No, recall where the origin is and how many inches wide the back wall is.

15. ## Re: Calc Word Problem. Please Help!!!

well the back wall is 99 inches wide, and the origin is at the lowest point of the ceiling, so would it be from 11 to 88

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