Adrenaline Rush
Registered User
can someone please help with #19 and #24 (ghost u explained it but i still dont understand) for the math part,, they just dont seem to click with me,,
thanks
thanks
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help please
- Thread starter Adrenaline Rush
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I'm assuming you mean problems 19 and 24, from the vaunted "Marine Corps study guide" Word document thats floating around?
19:
x=.5t(y-z)
You want to find this equation in terms of y.
x=.5t(y-z)
x=.5ty-.5tz
(by some property of multiplication)
x+.5tz=.5ty
(by adding .5tz to both sides)
(x+.5tz)/(.5t)=y
(dividing both sides by .5t)
(x/.5t)+(.5tz)/(.5t)=y
(by some property of addition. (a+b)/c == a/c + b/c.)
(x/.5t)+z=y
(canceled the denominator in the z part. (ab)/a=b.)
(2x)/t + z=y
This last set is (in part) x/(1/2). Dividing by something is the same as multiplying by the reciprocal. IE, 4/9 = 4*(1/9).
And also, I should note, that (2x)/t == 2x/t (so that it looks like it does in the answer
19:
x=.5t(y-z)
You want to find this equation in terms of y.
x=.5t(y-z)
x=.5ty-.5tz
(by some property of multiplication)
x+.5tz=.5ty
(by adding .5tz to both sides)
(x+.5tz)/(.5t)=y
(dividing both sides by .5t)
(x/.5t)+(.5tz)/(.5t)=y
(by some property of addition. (a+b)/c == a/c + b/c.)
(x/.5t)+z=y
(canceled the denominator in the z part. (ab)/a=b.)
(2x)/t + z=y
This last set is (in part) x/(1/2). Dividing by something is the same as multiplying by the reciprocal. IE, 4/9 = 4*(1/9).
And also, I should note, that (2x)/t == 2x/t (so that it looks like it does in the answer
For #24, you startout with:
|
|
x
|
|
|_____x_____|
and end up with:
|
|
|
x
|
|
|_____x_____|___4___|
So 4 feet of tarp are tacked onto a x-square tarp. This means that while one side changes, the other side stays the same.
So we know that the original area is base times height, or x*x. Our new "base" is (x+4), but our height is still x.
(x+4)x = x^2 + 4x
You could also look at this another way:
You still have the old tarp. Its area is x^2. The new part is x high, and 4 long. The new parts area is 4x. Add the two together, and you have x^2 + 4x.
|
|
x
|
|
|_____x_____|
and end up with:
|
|
|
x
|
|
|_____x_____|___4___|
So 4 feet of tarp are tacked onto a x-square tarp. This means that while one side changes, the other side stays the same.
So we know that the original area is base times height, or x*x. Our new "base" is (x+4), but our height is still x.
(x+4)x = x^2 + 4x
You could also look at this another way:
You still have the old tarp. Its area is x^2. The new part is x high, and 4 long. The new parts area is 4x. Add the two together, and you have x^2 + 4x.
Adrenaline Rush
Registered User
thank you rabbit, i appreciate your help!!!!
AllenAzali
Registered User
can someone help me with #6 in the math section
Which is true?
A. 2/25 > 1/10
B. 1/10 > 3/30
C. 2/28 < 3/35
D. 5/13 = 4/5
Are there any shortcuts to this problem. It take me like 5 minutes to convert them into decimals, are there any proportional experts out there that can offer advice?
Which is true?
A. 2/25 > 1/10
B. 1/10 > 3/30
C. 2/28 < 3/35
D. 5/13 = 4/5
Are there any shortcuts to this problem. It take me like 5 minutes to convert them into decimals, are there any proportional experts out there that can offer advice?
I did them in this order: A, B, D. I skipped C precisely because the conversion would've been too time-consuming. The first thing you should try to do in a multiple choice problem is get rid of options. Working against the clock, I just do the fastest ones first, and see what drops out.
As far as the math goes I can't really give you a trick. I did it the first way--but depending on how comfortable you are with mental math, the second method might be easier.
A) something times twenty-five is a nice multiple of ten. Two times twenty-five is fifty which is neatly divisible by ten.
B) as above. X*10 is neatly divisible by 30--X is 3.
C) skipped
D) 4/5 is close to a whole, 5/13 isn't even a half. False.
The above might be easier, or this:
If you take the inverse of these, you end up with easier denominators: remember to switch the test statement. After modifying them:
A) (25/2) < (10/1). 25/2 is a little more than 12, which is bigger than 10. false.
B) 10 is equal to 10. false.
C) 28/2 > 35/3. 28/2 is 14, but 35/3 is about 12. true.
D) 13/5 = 5/4. 13/5 is almost 3, but 5/4 is just more than 1. false.
As far as the math goes I can't really give you a trick. I did it the first way--but depending on how comfortable you are with mental math, the second method might be easier.
A) something times twenty-five is a nice multiple of ten. Two times twenty-five is fifty which is neatly divisible by ten.
B) as above. X*10 is neatly divisible by 30--X is 3.
C) skipped
D) 4/5 is close to a whole, 5/13 isn't even a half. False.
The above might be easier, or this:
If you take the inverse of these, you end up with easier denominators: remember to switch the test statement. After modifying them:
A) (25/2) < (10/1). 25/2 is a little more than 12, which is bigger than 10. false.
B) 10 is equal to 10. false.
C) 28/2 > 35/3. 28/2 is 14, but 35/3 is about 12. true.
D) 13/5 = 5/4. 13/5 is almost 3, but 5/4 is just more than 1. false.
AllenAzali
Registered User
Yea, I guess there is no quick trick for #6. I noticed that B was pretty straigt forward. Took your point to consider wholes and halfs with D. Inverse trick worked well with A. Which leaves C. Thanks again.
I beleve its the quick tricks that help the most, especially during a timed test.
For example on math section #28. On first impression I thought I had to figure out the numbers for all ranks then add them up for the total. But I also learned that you just add them up and divide by 2. For total head count.
#33 is also a doosie. Throw out the Sin, Cos, Tan. and use the distance/rate formula.
I beleve its the quick tricks that help the most, especially during a timed test.
For example on math section #28. On first impression I thought I had to figure out the numbers for all ranks then add them up for the total. But I also learned that you just add them up and divide by 2. For total head count.
#33 is also a doosie. Throw out the Sin, Cos, Tan. and use the distance/rate formula.
AllenAzali
Registered User
Can anybody remember the gouge for the monkey climbing the rope and the pendulum swinging questions found in test 1. I believe they were mechanical questions.
AllenAzali
Registered User
yea, maybe it was the elevator. What was the concept, basic pulley systems
Allen,
Did you get that pulley question figured out? I'm supposing that you had version 1 of the ASTB? I think that question was a mixture of a basic pulley question and an equilibrium question...with the monkey and whatever was on the other end of the rope being balanced.
Did you get that pulley question figured out? I'm supposing that you had version 1 of the ASTB? I think that question was a mixture of a basic pulley question and an equilibrium question...with the monkey and whatever was on the other end of the rope being balanced.
mimisoko9,
Ok here we go:
It's actually a pretty straight forward problem once you get through the confusing wording.
-For all real numbers x and y, x*y = y(x+1)
-If -4*j = -6 then j=
#1. Well, from looking at the problem we can figure out that
-4 is x and j is y.
#2. Since #1 above is true then -6 = y(x+1).
#3. Since #2 is true then can figure out that -6 = y(-4*1) (don't forget that y is really j but I am using y to make it easier). Then we just solve like a regular algebra problem.
-6 = -4y+1y
-6 = -3y
-6/-3 = -3y/-3
2 = y
and then since y is j ..... j = 2 or answer c.
I hope that wasn't too confusing!!
Peace,
-Spin
Ok here we go:
It's actually a pretty straight forward problem once you get through the confusing wording.
-For all real numbers x and y, x*y = y(x+1)
-If -4*j = -6 then j=
#1. Well, from looking at the problem we can figure out that
-4 is x and j is y.
#2. Since #1 above is true then -6 = y(x+1).
#3. Since #2 is true then can figure out that -6 = y(-4*1) (don't forget that y is really j but I am using y to make it easier). Then we just solve like a regular algebra problem.
-6 = -4y+1y
-6 = -3y
-6/-3 = -3y/-3
2 = y
and then since y is j ..... j = 2 or answer c.
I hope that wasn't too confusing!!
Peace,
-Spin
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