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nahid078: Master | Next Rank: 500 Posts; Posts: 105; Joined: Tue May 13, 2014 10:41 am; Thanked: 2 times; Followed by:1 members

Lottery

by nahid078 » Thu Jul 02, 2015 3:01 am

This is how Edward's lotteries work. First 9 different numbers are selected. tickets with exactly 6 of the nine numbers randomly selected and printed such that no two tickets have the same set of numbers. Finally, the winning ticket is the one containing the 6 numbers drawn from the 9 randomly. There is exactly one winning ticket in the lottery system. How many tickets can the lottery system print?

1) 9p6
2) 9p3
3) 9c9
4) 9c6
5) 6^9

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Source: Beat The GMAT — Problem Solving | Thu Jul 02, 2015 3:01 am

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by [email protected] » Thu Jul 02, 2015 10:23 am

Hi nahid078,

What is the source of this question? I ask because it's poorly-worded and you would benefit by working with better material. There are plenty of study materials available that are more in-line with what you'll see on the Official GMAT.

GMAT assassins aren't born, they're made,
Rich

Contact Rich at [email protected]

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nahid078: Master | Next Rank: 500 Posts; Posts: 105; Joined: Tue May 13, 2014 10:41 am; Thanked: 2 times; Followed by:1 members

by nahid078 » Thu Jul 02, 2015 10:48 am

I have found it from a book named "GMAT math bible". It is published by NOVA. I didn't understand it's explanation properly so posted it here.

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Brent@GMATPrepNow: GMAT Instructor; Posts: 16207; Joined: Mon Dec 08, 2008 6:26 pm; Location: Vancouver, BC; Thanked: 5254 times; Followed by:1268 members; GMAT Score:770

by Brent@GMATPrepNow » Thu Jul 02, 2015 11:04 am

In addition to being poorly-worded, the question also has problems with the answer choices.
The test-makers don't expect you to know what 9P6 and 9C6 mean.
In fact, in its math syllabus, the OG uses a different notation for combinations.

Cheers,
Brent

Brent Hanneson - Creator of GMATPrepNow.com

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nikhilgmat31: Legendary Member; Posts: 518; Joined: Tue May 12, 2015 8:25 pm; Thanked: 10 times

by nikhilgmat31 » Fri Jul 03, 2015 2:49 am

please provide a simple solution

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talaangoshtari: Master | Next Rank: 500 Posts; Posts: 154; Joined: Wed May 21, 2014 4:29 am; Thanked: 8 times; Followed by:1 members

by talaangoshtari » Fri Jul 03, 2015 3:31 am

Suppose we have two letters A and B. We can have 2 sets,
AB, and BA. According to the question, no two tickets have the same sets. This means that if I have a ticket that have the letters BA on it, then I cannot have a ticket AB. In other words,
the order does not matter.
In this question, I assume that there is a set of numbers 123456 on ticket 1. Any other combination cannot be on other tickets. 123465 for example cannot be on another ticket...
So the coreect answer is 9C6