Math Combination Question

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Dublin08: Newbie | Next Rank: 10 Posts; Posts: 1; Joined: Tue Aug 23, 2011 8:25 am

by Dublin08 » Tue Aug 23, 2011 8:29 am

Can anyone help explain how to get the answer to this question

There are 12 x songs in a list and each student has to select 2 x favourite songs from this list, each song is selected 4 x times - how many students were asked to parttake in this exercise?

thanks

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Source: Beat The GMAT — Problem Solving | Tue Aug 23, 2011 8:29 am

Frankenstein: Legendary Member; Posts: 1448; Joined: Tue May 17, 2011 9:55 amFollowed by: 53 members; Location: India; Thanked: 375 times

by Frankenstein » Tue Aug 23, 2011 8:36 am

Hi,
There are 12x songs and each song is selected 4x times. So, total selections = 12x * 4x.
Each student selects 2x songs.
So, number of students = 12x * 4x/2x = 24x.

Cheers!

Things are not what they appear to be... nor are they otherwise

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saketk: Legendary Member; Posts: 608; Joined: Sun Jun 19, 2011 11:16 amFollowed by: 8 members; Thanked: 37 times

by saketk » Wed Aug 24, 2011 9:09 am

Dublin08 wrote:Can anyone help explain how to get the answer to this question

There are 12 x songs in a list and each student has to select 2 x favourite songs from this list, each song is selected 4 x times - how many students were asked to parttake in this exercise?

thanks

To start with consider that out of 12 songs each student has to
Select 2 songs and every song can be selected only once. I am telling you this to ezxplain you the logic
Now if you want to find the number of people the simply multiply 12 by 1 and divide by 2. You will get 6 as the answer. Why this? Simply because a song selected once is out of next selection process. Now you just have to replicate this concept in the given question. Your answer will be 24 (6*4)

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