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Elena89: Senior | Next Rank: 100 Posts; Posts: 35; Joined: Sun Jul 31, 2011 9:39 pm; Thanked: 2 times; Followed by:1 members

OG-12 DS

by Elena89 » Tue Dec 20, 2011 6:01 am

Is the number of members of Club X greater than the number of members of Club Y ?

(1) Of the members of Club X, 20 percent are also
members of Club Y.
(2) Of the members of Club Y, 30 percent are also
members of Club X.

[spoiler]
How is the correct answer (C) ?[/spoiler]

Quote

Source: Beat The GMAT — Data Sufficiency | Tue Dec 20, 2011 6:01 am

rijul007: Legendary Member; Posts: 588; Joined: Sun Oct 16, 2011 9:42 am; Location: New Delhi, India; Thanked: 130 times; Followed by:9 members; GMAT Score:720

by rijul007 » Tue Dec 20, 2011 6:13 am

Elena89 wrote: How is the correct answer (C) ?

No of members in Club X = x
No of members in club Y = y

Combining (1) and (2)
20% of x = 30% of y
x = 3y/2
x > y

Quote

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Anurag@Gurome: GMAT Instructor; Posts: 3835; Joined: Fri Apr 02, 2010 10:00 pm; Location: Milpitas, CA; Thanked: 1854 times; Followed by:523 members; GMAT Score:770

by Anurag@Gurome » Tue Dec 20, 2011 7:06 am

Elena89 wrote:Is the number of members of Club X greater than the number of members of Club Y ?

(1) Of the members of Club X, 20 percent are also
members of Club Y.
(2) Of the members of Club Y, 30 percent are also
members of Club X.

[spoiler]
How is the correct answer (C) ?[/spoiler]

Let the total number of members of Club X = X
and the total number of members of Club Y = Y
People who are members of both clubs X and Y = XY

(1) XY = 20% of X or XY = 0.2X
If X = 100, then XY = 20 but we do not anything about the members of club Y; NOT sufficient.

(2) XY = 30% of Y or XY = 0.3Y
If Y = 100, then XY = 30 but here but we do not anything about the members of club X; NOT sufficient.

Combining (1) and (2), XY = 0.2X = 0.3Y, which implies X = 3Y/2, so X is greater than Y; SUFFICIENT.

The correct answer is C.

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