GMAT Math Review
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 beatthegmat
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Decent review of GMAT math topics...
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 sanju09
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quite handybeatthegmat wrote:Decent review of GMAT math topics...
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 harsh.champ
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Thanks eric.beatthegmat wrote:Decent review of GMAT math topics...
Definitely appreciate it.
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I had 2 questions in going over this review. The example of problems involving variables mentions 1,800 newspapers, however the solution and answers reflect 18,000. Did I miss something or was this just a typo? Here is the problem in question...
At a certain printing plant each of m machines print 6 newspapers in every s seconds. If all machines work together and independently without interruption
How many minutes will it take to print 1800 newspapers?
a) 180 s / m
b) 50 s / m
c) 50ms
d) ms / 50
e) 300 m / s
Solution:
Let m = 2 and s = 1
Since each of m machines prints 6 newspapers in s seconds
So 2 machines prints 2*6 newspapers in 1 second
That is 12*60 newspapers in one minute.
720  1 minute
18000 ?
18000 / 720
= 25[/i]
The set theory example has unfortunately gotten me a little confused. If 10% of the red toys are small and 40% of the overall toys are red then wouldn't it represent (40% x 10% =4% of the overall total). The question did not say 10% of the overall total is red and small so how is that represented in the solution? The example is listed below...
In a certain production lot 40% of the toys are red and remaining toys are green. Half of the toys are small and half are large. If 10% of the red toys are small, 40 toys are green and large. How many of the toys are red and large?
Large Small Total
Red 30 10 40
Green 20 40 60
Total 50 50 100
Given is 40 toys are green and large
20% of total toys = 40
20 * n / 100 = 40 n = 200
How many toys are red and large?
30 % of 200 = 60
Please keep up the great work and thank you for all your help.
At a certain printing plant each of m machines print 6 newspapers in every s seconds. If all machines work together and independently without interruption
How many minutes will it take to print 1800 newspapers?
a) 180 s / m
b) 50 s / m
c) 50ms
d) ms / 50
e) 300 m / s
Solution:
Let m = 2 and s = 1
Since each of m machines prints 6 newspapers in s seconds
So 2 machines prints 2*6 newspapers in 1 second
That is 12*60 newspapers in one minute.
720  1 minute
18000 ?
18000 / 720
= 25[/i]
The set theory example has unfortunately gotten me a little confused. If 10% of the red toys are small and 40% of the overall toys are red then wouldn't it represent (40% x 10% =4% of the overall total). The question did not say 10% of the overall total is red and small so how is that represented in the solution? The example is listed below...
In a certain production lot 40% of the toys are red and remaining toys are green. Half of the toys are small and half are large. If 10% of the red toys are small, 40 toys are green and large. How many of the toys are red and large?
Large Small Total
Red 30 10 40
Green 20 40 60
Total 50 50 100
Given is 40 toys are green and large
20% of total toys = 40
20 * n / 100 = 40 n = 200
How many toys are red and large?
30 % of 200 = 60
Please keep up the great work and thank you for all your help.
Yes the question is typed mistakenly.It must time to print 18000 newspapers.
s sec=6 Newspapers
1 sec =6/s Newspapers
m machines print m*6/S in 1 sec
1 sec=m*6/s
60 sec=m*360/s
m*360/s=1 min
18000=?
18000=X*m*360/S
X=18000*S/m*360
X=50S/m
s sec=6 Newspapers
1 sec =6/s Newspapers
m machines print m*6/S in 1 sec
1 sec=m*6/s
60 sec=m*360/s
m*360/s=1 min
18000=?
18000=X*m*360/S
X=18000*S/m*360
X=50S/m
Anand

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Thanks for the quick response. I thought I was going crazy. In my post I had a second question as well that may have gotten lost in the shuffle so I copied it from my previous post. Your help is greatly appreciated.
Mike
The set theory example has unfortunately gotten me a little confused. If 10% of the red toys are small and 40% of the overall toys are red then wouldn't it represent (40% x 10% =4% of the overall total). The question did not say 10% of the overall total is red and small so how is that represented in the solution? The example is listed below...
In a certain production lot 40% of the toys are red and remaining toys are green. Half of the toys are small and half are large. If 10% of the red toys are small, 40 toys are green and large. How many of the toys are red and large?
Large Small Total
Red 30 10 40
Green 20 40 60
Total 50 50 100
Given is 40 toys are green and large
20% of total toys = 40
20 * n / 100 = 40 n = 200
How many toys are red and large?
30 % of 200 = 60
Mike
The set theory example has unfortunately gotten me a little confused. If 10% of the red toys are small and 40% of the overall toys are red then wouldn't it represent (40% x 10% =4% of the overall total). The question did not say 10% of the overall total is red and small so how is that represented in the solution? The example is listed below...
In a certain production lot 40% of the toys are red and remaining toys are green. Half of the toys are small and half are large. If 10% of the red toys are small, 40 toys are green and large. How many of the toys are red and large?
Large Small Total
Red 30 10 40
Green 20 40 60
Total 50 50 100
Given is 40 toys are green and large
20% of total toys = 40
20 * n / 100 = 40 n = 200
How many toys are red and large?
30 % of 200 = 60
40% of toys are Red
10% of red toys are small.The word seems to be awkward.Got confused here.
10% of red toys small means 10% small and 30% large.
10% of overall red toys small means 4% small.
10% of red toys are small.The word seems to be awkward.Got confused here.
10% of red toys small means 10% small and 30% large.
10% of overall red toys small means 4% small.
Anand