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ps questions from gmatprep

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Master | Next Rank: 500 Posts
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ps questions from gmatprep

by xcise_science » Sat Dec 01, 2007 4:55 pm
Q36
I couldn't quite figure out what topic was tested in this problem.
Image
answer is D

Q17
I thought this was a simple rate problem, but I got it wrong anyway.

Image
answer is E

Q34

Image
answer is D
Thanks
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Junior | Next Rank: 30 Posts
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Q17

by oct07 » Sun Dec 02, 2007 12:59 pm
Q17

Case 1:
t1 = 5/30=1/6
t2 = (x-5) / 60
t = t1+t2 = 1/6 + (x-5)/60 = (x+5)/60

Case 2:
t = x/60

Paraphrase the Qs:
[ (t1+t2) - t ] / t *100% =[ (x+5)/60 - x/60 ] / x/60 * 100%
= 5/x * 100% = 500%/x

As E

Please correct if I am wrong.
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by lawalx » Sun Dec 02, 2007 2:51 pm
q34

pr A + Pr B + Pr C

Pr A = .30

Pr B = Pr. Not A * Pr B
= .70 * .30 = .21

Pr C = Pr Not A* Pr Not B * Pr C
= .70 * .70 * .30 = .147

add em up = .657
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by xcise_science » Sun Dec 02, 2007 3:52 pm
hi thanks, but i don't understand.

i don't even understand what the p()=.30 represents.

pr A + Pr B + Pr C
Pr A = .30
Pr B = Pr. Not A * Pr B <== this is not clear either, why did you multiply by p(b)?
= .70 * .30 = .21
Pr C = Pr Not A* Pr Not B * Pr C
= .70 * .70 * .30 = .147
add em up = .657
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Master | Next Rank: 500 Posts
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by xcise_science » Sun Dec 02, 2007 4:01 pm
Q17,
hello,

how did you get (x+5)/60 here?
t = t1+t2 = 1/6 + (x-5)/60 = (x+5)/60

also, can you explain your calculations for how you 5/x here:
[ (t1+t2) - t ] / t *100% =[ (x+5)/60 - x/60 ] / x/60 * 100%
= 5/x * 100% = 500%/x


And was this a percent increase question? would it have been worthwhile to plug in numbers instead of working with x?

thanks!
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