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 Post subject: GMAT Test Prep QsPosted: Sun Jul 19, 2009 8:40 pm

Joined: Fri May 29, 2009 9:04 pm
Posts: 3
Here are a list of questions that I got incorrect on the practice test. For some reason, there are no explanations for the answers. I'd appreciate if you can provide insight. Thanks!

1)
+ | X Y Z
--|-----------
4 | 1 -5 m
e | 7 n 10
f | 2 -4 5
_____________

In the addition table above, what is the value of m+n? The answer is 5. not sure how to get it?

2) For all positive integers m, m = 3m where m is odd and m = (1/2)m where m is event. Which of the following is equal to 9 x 6?

The way I did it, was multipled 9 (odd) by 3 and multplied 6 (even) by 1/2 and the product = 81.

3. Circular gears P&Q start rotating @ constant speeds. Gear P makes 10 revolutions / min and gear Q makes 40 revolutions per minute. how many seconds after the gears start rotating will gear Q have made exactly 6 more revolutions than gear P?

Don't know how to get that.

4. If r and s are integers and rs+r is odd, which of the following must be even?
a) r
b) s
c) r+s
d) rs-r
e) r^2 + s

Need explanation.

5. For a certain exam, a score of 58 was 2 Standard Deviations (SD) below mean and a score of 98 was 3 SD below mean. What is the mean?
Need explanation

6) IN an xy plan, at what two points does the graph of y = (x+a) (x+b) intersect x axis.
1) a+b = -1
2) the graph intersects y axis at (0,-6)

7) The sum of the integers in list S is the same as the sum of the integers in list T. Does S contain more integers than T?

1) The average mean of integers in S is less than the average mean of integers in T
2) The median of the integers in S is greater than the median of integers in T

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 Post subject: Re: GMAT Test Prep QsPosted: Mon Jul 20, 2009 4:42 pm

Joined: Thu Feb 12, 2009 6:32 pm
Posts: 497
Sure.
Normally, I’d suggest, for a long list of questions like this, that you contact the help email, as the forum isn’t ideal for lists.
But here you go.
#1.
Notice that it’s an “addition table.” This means that if we take the number or letter at the top of the column and the number or letter to the left of the row, we’ll get a resulting sum equal to the intersection point.
For example, we know that x + 4 = 1. This means x = -3.
From this point, we can find everything in the x column.
If x is -3, and x+e = 7, then -3 + e = 7, so e = 10
Using the same process, we find that f=5.
Then, go over to the column containing the n.
F+y = -4. We know that f is 5, so 5 + y = -4, and y = -9
If y=-9 and e=10, and y+e = n, then -9 + 10 = n, or n=1.
We The go to the last column.
F + z = 5. We know that f is 5, so 5 + z = 5, which means z=0.
Z + 4 = m. Since z=0, we know that m=4.
This means m+n = 4 +1, or 5.

#2. I think you have some notation wrong here. There should be a box around the m, or something like that, and the same goes for the answer choices. If you’ll send me a screen shot of this one, I can answer it for you. (help@veritasprep.com)

#3.
If P makes 10 rev/minute, then it makes 1/6 revolution per second.
If Q makes 40 revs per minute, then it makes 2/3 rev per second.
We’ll use those rates, since our final answer deals with seconds.

The time for both is the same, T.
The number of revolutions made by P in time T is T * 1/6 or T/6.
The number made by Q, in turn, is 2T/3
We want Q to be 6 higher than P, so our formula is:
T/6 + 6 = 2T/3
Solving for T, we get
T/6 + 36/6 = 4T/6
36 = 3T
12 = T

#4
We know that odd + even = odd, even + even = even, and odd + odd = odd.
So for rs + r to be odd, one of the terms must be odd and another must be even.
If r is even, then both rs and r are even, so this can’t be the case.
If s is even, then rs is even, and r is odd, and this one works.

#5
I think you’ve picked up a typo in this one, or have made a transcription error.
If 58 is below the mean by 2 standard deviations, then 98 can’t be even further below. Perhaps 98 represents some number above the mean??

#6.
A graph of a line will intersect the x axis when y=0.
So, in this case, we can set y=0 and we have
0 = (x+a)(x+b)
This means it intersects the x axis at –a and at –b.
Statement 1 doesn’t give us enough on its own.
Statement 2 tells us that one of –a or –b is -6. We don’t know the other one, though.
Together, however, we know that one of the two is -6, and that a+b = -1, so the other point must be 5.
We don’t have to know which is a and which is b, in this case. So together, the statements are sufficient, and our answer is C.

#7.
If the sum of the two lists is identical, but the means are different, it means one of the lists has more members.
For example, if the sum of each is 100, but there are 5 members of S and 4 members of T, then the average of S will be 20, and the average of T will be 25.
The list with fewer numbers will have a higher mean.
Thus, (1) tells us that S has more numbers, and is sufficient.
(2) tells us nothing useful, as median and mean are rarely correlated.

Veritas Help

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 Post subject: Re: GMAT Test Prep QsPosted: Mon Jul 20, 2009 8:52 pm

Joined: Fri May 29, 2009 9:04 pm
Posts: 3
Thanks for the answers! I've followed up with an email to the help alias for the other Qs.

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