2007 district questions

[smeag]

can someone please provide explanations for: 26, 27, 36, 37, 38
thanks!
2007F

[Shawn]

26)
Find Weight to Useable Unit:
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Find Total Volume of Roll:
[unparseable or potentially dangerous latex formula]
Divide Total Volume by Volume/Sheet to get Sheets:
[unparseable or potentially dangerous latex formula]
[unparseable or potentially dangerous latex formula]
[unparseable or potentially dangerous latex formula]
27)
Area of Track Interior:
Semicircles congruent, so put them together:
[unparseable or potentially dangerous latex formula]
[unparseable or potentially dangerous latex formula]
[unparseable or potentially dangerous latex formula]
[unparseable or potentially dangerous latex formula]
[unparseable or potentially dangerous latex formula]
Width is 2 times the radius of circles length is given:
[unparseable or potentially dangerous latex formula]
[unparseable or potentially dangerous latex formula]
[unparseable or potentially dangerous latex formula]
Area of Football Field:
[unparseable or potentially dangerous latex formula]
[unparseable or potentially dangerous latex formula]
[unparseable or potentially dangerous latex formula]
[unparseable or potentially dangerous latex formula]
[unparseable or potentially dangerous latex formula]
[unparseable or potentially dangerous latex formula]
[unparseable or potentially dangerous latex formula]
36) Number of glasses per batch:
[unparseable or potentially dangerous latex formula]
[unparseable or potentially dangerous latex formula]
Expenses+Desired Profit=Needed Revenue
[unparseable or potentially dangerous latex formula]
[unparseable or potentially dangerous latex formula]
Needed Revenue/Units Sold=Needed Selling Price
[unparseable or potentially dangerous latex formula]
[unparseable or potentially dangerous latex formula]
37) Will solve fully later, but hint: How much many degrees over relative rate.
Solution: First find distance to catch up once, then just add 720
Positions
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[unparseable or potentially dangerous latex formula]
Distance to go:
Minute hand has to catch hour hand so:
[unparseable or potentially dangerous latex formula]
Add in 720 for touch third time (1st is just catch up next all way next all way)
[unparseable or potentially dangerous latex formula]
Divide by related rate:
[unparseable or potentially dangerous latex formula]
And then look at the key because you didn't read the answer blank and realize to convert....
[unparseable or potentially dangerous latex formula]
[unparseable or potentially dangerous latex formula]

[Shawn]

38) Don't care about dimensions (unless you magically know the density)
Find water weight after drying:
[unparseable or potentially dangerous latex formula]
Find weight of waterless wood before and after drying
[unparseable or potentially dangerous latex formula]
Now since this is 60% of weight before, just divide by 0.6
[unparseable or potentially dangerous latex formula]
[unparseable or potentially dangerous latex formula]
bw=0.4*(89.965+bw)
I am doing something wrong apparently.... someone else can have a shot.

[smeag]

thanks for all you help, it's just that the 36-38 problems continue to annoy me...

[smeag]

sorry, shawn but I tried the scaling problem and I got it wrong. For example, since it was in squared, I thought it should be:

18^2 / 12 = x^2 / 20

can someone please explain why I got the wrong answer?

also, I tried the solver and got no sign change error

also, number 40 geometry sorry I won't ask this again..

[Shawn]

Same test?
07f-46)
Volume is exhales (since the word is filtered...) surface area is surface area.
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[unparseable or potentially dangerous latex formula]
07f-48)
[unparseable or potentially dangerous latex formula]
[unparseable or potentially dangerous latex formula]
If you use an HP, I have no clue about your error.

[smeag]

could you please clarify number 46, I don't understand where you got the 2/3 from. Please do the whole problem in steps, if you don't mind...

[Shawn]

46) Generally how to do scaling problems:
1. Read the problem.
2. Determine the independent and dependent variable
3. Determine the dimension of the variable (volume is cubic surface area square length linear varies "_____" (such as with the .8 power of cross section or something))
4. Take the independent variable to linear
5. Take result of 4 to dependent scale
Using the problem:
You are given "pulses of air" (wonderful filter) and surface area. "Pulses of air" is volume (cubic) (you "pulse in" so much air per "pulse") and obviously surface area is square. So to get number of "pulses of air" to surface area, what do you scale by? First take "pulses of air" to linear by cube rooting (1/3 power) and then square this value. What you were trying to do is say surface area is the square of volume, no it is the square of length (in this case radius). So first get the volume to a one-dimension unit and then covert this to surface area.
Therefore,
12^(2/3) and 32^(2/3) are the scaled surface area factors
Hopefully this helped, if not I need to know what you don't understand in more detail.