Find all School-related info fast with the new School-Specific MBA Forum

 It is currently 05 May 2015, 05:09

### GMAT Club Daily Prep

#### Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# Each of the integers from 0 to 9, inclusive, is written on a

Author Message
TAGS:
Manager
Joined: 21 Jun 2004
Posts: 239
Followers: 1

Kudos [?]: 1 [0], given: 0

Each of the integers from 0 to 9, inclusive, is written on a [#permalink]  07 May 2005, 00:06
Each of the integers from 0 to 9, inclusive, is written on a separate slip of blank paper and the ten slips are dropped into a hat. If the slips are then drawn one at a time without replacement, how many must be drawn to ensure that the numbers on two of the slips drawn will have a sum of 10?

3

4

5

6

7

--------------

I did get the ans right, but I hoping there's a better method than the one I used.
Senior Manager
Joined: 19 Feb 2005
Posts: 487
Location: Milan Italy
Followers: 1

Kudos [?]: 11 [0], given: 0

with the integers from 0 to 9, you can add 10 with
1+9
2+8
3+7
4+6
other numbers are 0,5

we should find a combination of 7 6 5 4 or 3 that does not add 10.
I started from 5 -> 9 8 7 6 5 (pick one number from first/second column and 0 or 5)
now 6-> pick one number from first/second column and both 0 and 5
0 5 9 8 7 6 or 0 5 1 2 3 4
7 is the answer because you pick
0 and 5 first
6 7 8 9 OR 1 2 3 4
next number will necessarily lead to 10 as a sum
VP
Joined: 26 Apr 2004
Posts: 1225
Location: Taiwan
Followers: 2

Kudos [?]: 167 [0], given: 0

sorry, Could not get it.

Would you explain more explicitly?

thanks
CIO
Joined: 09 Mar 2003
Posts: 464
Followers: 2

Kudos [?]: 34 [0], given: 0

I think it's 7.

You have to just assume the worst - that you won't get 10 until it's absolutely impossible to get anything else.

So what makes ten?

1-9
2-8
3-7
4-6

That's it. So what if the first number you choose is 0? You'll never get ten. What if the next one is 5? Same problem. So now you've chosen 2 numbers already, and no 10.

Then, what if you pick all the next numbers that don't have a partner? Let's say you pick 1,2,3,4 in a row. None of your number now will add up to 10, and you've chosen 6 numbers.

What's left? The 4 partners to 1,2,3,4 - so the next number you choose, whatever it is, will definately match with one of them to make 10.

So on the 7th pull, you've got it.
VP
Joined: 26 Apr 2004
Posts: 1225
Location: Taiwan
Followers: 2

Kudos [?]: 167 [0], given: 0

nice explanation, ian777.

thanks
Director
Joined: 31 Aug 2004
Posts: 606
Followers: 3

Kudos [?]: 43 [0], given: 0

Agree with you guys. You have to skip 0 and 5 whixh do not lead to any correct sum. Then the 4 first component of this "10" sum. The following one must at least complete one of the possible sums.
Manager
Joined: 21 Jun 2004
Posts: 239
Followers: 1

Kudos [?]: 1 [0], given: 0

ans is indeed 7, and i too followed the very same method .

thanks all !
VP
Joined: 13 Jun 2004
Posts: 1122
Location: London, UK
Schools: Tuck'08
Followers: 7

Kudos [?]: 31 [0], given: 0

Also found 7

0,1,2,3,4,5 and then the next draw will give you a number which, added to the previous one, will give you 10.
Intern
Joined: 06 May 2005
Posts: 17
Followers: 1

Kudos [?]: 10 [0], given: 0

LOok at this way:

There are 6 numbers (0,1,2,3,4,5) forming a set in which any two numbers do not add up to 10.

So, in the worst case scenario (if you were to be absolutely sure that there are 2 numbers that add to 10), You need to pick these 6 numbers + one more. So, the answer is 7.

-Srinivas.

chunjuwu wrote:
sorry, Could not get it.

Would you explain more explicitly?

thanks
VP
Joined: 25 Nov 2004
Posts: 1495
Followers: 6

Kudos [?]: 38 [0], given: 0

ian7777 wrote:
I think it's 7.

absoulately. but for me sometimes 0 is a killer.....
Similar topics Replies Last post
Similar
Topics:
7 Each of the integers from 0 to 9, inclusive, is written on a 6 11 Apr 2012, 08:26
Each of the integers from 0 to 9, inclusive, is written on a 2 24 Jul 2011, 02:48
2 Each of the integers from 0 to 9, inclusive, is written on a 7 17 Aug 2008, 01:51
Each of the integers from 0 to 9, inclusive, is written on a 1 25 Jun 2007, 14:00
Each of the integers from 0 to 9, inclusive, is written on a 4 16 Oct 2005, 00:57
Display posts from previous: Sort by