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Need help with these DS problems...Thanks.

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Need help with these DS problems...Thanks.

by strain15 » Thu Jun 16, 2011 9:25 pm
1. What is the value of X?

(1) 4X + 18 = 2X + 22
(2) 8/X + 14 = 6/X +16

Since (1) and (2) gives a different X value, what would the answer be?

2. There are three sprinters on a racetrack. How much time will it take all three to finish a 800 meters race?

(1) The first runner can run the fastest, he runs at a 110% of the slower runner.
(2) The slowest runner runs at a constant speed of 7 meters per second.

3. A town rules require each house to have at least a ping-ping table or a soccer table. If there are 50 houses in this town, how many houses carry both types of tables?

(1) The number of houses that have a ping-pong table only is 20.
(2) The number of houses that have a soccer table is 40.


Can anyone please help me on the questions? Thank you very much.
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Source: — Data Sufficiency |

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by Anurag@Gurome » Thu Jun 16, 2011 9:33 pm
Question Number 1:
strain15 wrote:What is the value of X?

(1) 4X + 18 = 2X + 22
(2) 8/X + 14 = 6/X +16
Ideally the statements of a good DS question do not contradict each other. What is the source of the question?
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by amit2k9 » Thu Jun 16, 2011 9:35 pm
1 x=18 and x=19, but the question is asking to determine the value of x. so sufficient.
D it is.
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by amit2k9 » Thu Jun 16, 2011 9:37 pm
2 a fastest runner time = slowest runner time/ 1.1. not sufficient, as the middle runner speed is not given.

b not sufficient as no values for middle and fastest speed runners given.

a+b not sufficient as middle runner speed not given.

E it is.
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by Anurag@Gurome » Thu Jun 16, 2011 9:38 pm
Question Number 2:
strain15 wrote:There are three sprinters on a racetrack. How much time will it take all three to finish a 800 meters race?

(1) The first runner can run the fastest, he runs at a 110% of the slower runner.
(2) The slowest runner runs at a constant speed of 7 meters per second.
The time taken by the slowest runner will determine the time it will take all three to finish the race. hence, we need to know the speed of the slowest runner.

Statement 1: No information about the speed of the slowest runner.

Not sufficient

Statement 2: We know the speed of the slowest runner.

Sufficient

The correct answer is B.
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by Frankenstein » Thu Jun 16, 2011 9:42 pm
Hi,
Q1)Generally, GMAT question should give the same result. As we are getting different values, you can consider it a non-GMAT question. But, if you are to choose an option you must choose D.

Q2)Do they start simultaneously or are they running one after the other? Not clear. If they start simultaneously, do we need to find the sum of their times taken or the time by which everyone finishes. This is also not clear. GMAT questions will be much clear than this.
From(1): No info. abt absolute speeds
From(2): No info. about absolute speed of second runner

Q3)n(AuB) =50. We need to find n(AnB)
From(1): n(A)-n(AnB) = 20
Not sufficient
From(2): n(B) = 40
Not sufficient
Both(1)&(2): n(A)-n(AnB)+n(B) = 20+40 =60 i.e. n(AuB) = 60
But n(AuB) is given 50
Doesn't match

I think there should not be 'only' in statement (1)

I think the source from which you have taken these questions have many questions which are not nicely framed. Please post the name of the source.
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by amit2k9 » Thu Jun 16, 2011 9:43 pm
3

table is

p !p

s 20 20 40

!s 10 0 10 no soccer and pingpong = 0 here.

total 50

a+b is sufficient.

hence C it is.
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by amit2k9 » Thu Jun 16, 2011 9:46 pm
Yes for question 2 it has to be mentioned clearly whether its the total time or the max time taken.

For max time taken B is sufficient.

For total time it has to be sum of all the 3 times taken together.
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