It is currently 18 Oct 2017, 00:43

### 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

# There are 6 cards numbered from 1 to 6. They are placed into

Author Message
Current Student
Joined: 11 May 2008
Posts: 555

Kudos [?]: 222 [0], given: 0

There are 6 cards numbered from 1 to 6. They are placed into [#permalink]

### Show Tags

09 Sep 2008, 05:46
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

There are 6 cards numbered from 1 to 6. They are placed into a box, and then one is drawn and put back and then another card is drawn and put back. What is the probability that one of the cards was 5 if the sum of the two was 8?

1
2/3
1/2
2/5
1/5

Kudos [?]: 222 [0], given: 0

SVP
Joined: 17 Jun 2008
Posts: 1535

Kudos [?]: 279 [0], given: 0

### Show Tags

09 Sep 2008, 05:56

The first card could be a 5 or 3. The second card needs to be either 3 or 5 respectively.

Thus, probability of first card being 5 and second card being 3 = 1/6 + 1/6 = 1/3
Similarly, probability of first card being 3 and second card being 5 = 1/6 + 1/6 = 1/3

Combining both, it should be 1/3 + 1/3 = 2/3.

Kudos [?]: 279 [0], given: 0

SVP
Joined: 07 Nov 2007
Posts: 1792

Kudos [?]: 1058 [0], given: 5

Location: New York

### Show Tags

09 Sep 2008, 06:40
arjtryarjtry wrote:
There are 6 cards numbered from 1 to 6. They are placed into a box, and then one is drawn and put back and then another card is drawn and put back. What is the probability that one of the cards was 5 if the sum of the two was 8?

1
2/3
1/2
2/5
1/5

possible combinations:
3,5
5,3
2,6
6,2
4,4

probability= 2/5
_________________

Smiling wins more friends than frowning

Kudos [?]: 1058 [0], given: 5

Current Student
Joined: 11 May 2008
Posts: 555

Kudos [?]: 222 [0], given: 0

### Show Tags

09 Sep 2008, 08:15
i thought the ans should be 1/6*1/6 + 1/6*1/6.

there are totally 6 ways of picking up the cards right?
thats what is the definiton of possible cases. its possible to pick up any of the 6 cards right?

Kudos [?]: 222 [0], given: 0

SVP
Joined: 07 Nov 2007
Posts: 1792

Kudos [?]: 1058 [0], given: 5

Location: New York

### Show Tags

09 Sep 2008, 08:31
arjtryarjtry wrote:
i thought the ans should be 1/6*1/6 + 1/6*1/6.

there are totally 6 ways of picking up the cards right?
thats what is the definiton of possible cases. its possible to pick up any of the 6 cards right?

Read the question again.. and ...again
What is the probability that one of the cards was 5 if the sum of the two was 8?
_________________

Smiling wins more friends than frowning

Kudos [?]: 1058 [0], given: 5

SVP
Joined: 17 Jun 2008
Posts: 1535

Kudos [?]: 279 [0], given: 0

### Show Tags

09 Sep 2008, 10:24
x2suresh wrote:
arjtryarjtry wrote:
There are 6 cards numbered from 1 to 6. They are placed into a box, and then one is drawn and put back and then another card is drawn and put back. What is the probability that one of the cards was 5 if the sum of the two was 8?

1
2/3
1/2
2/5
1/5

possible combinations:
3,5
5,3
2,6
6,2
4,4

probability= 2/5

Thanks x2suresh. I wish I could think probability problems in these simple terms....not sure why I have got fobia to probability.

Kudos [?]: 279 [0], given: 0

Current Student
Joined: 11 May 2008
Posts: 555

Kudos [?]: 222 [0], given: 0

### Show Tags

09 Sep 2008, 10:26
x2suresh wrote:
arjtryarjtry wrote:
i thought the ans should be 1/6*1/6 + 1/6*1/6.

there are totally 6 ways of picking up the cards right?
thats what is the definiton of possible cases. its possible to pick up any of the 6 cards right?

Read the question again.. and ...again
What is the probability that one of the cards was 5 if the sum of the two was 8?

hmm..
i still think that the problem is not well worded...

Kudos [?]: 222 [0], given: 0

Manager
Joined: 03 Jun 2008
Posts: 133

Kudos [?]: 45 [0], given: 0

Schools: ISB, Tuck, Michigan (Ross), Darden, MBS

### Show Tags

09 Sep 2008, 11:43
arjtryarjtry wrote:
x2suresh wrote:
arjtryarjtry wrote:
i thought the ans should be 1/6*1/6 + 1/6*1/6.

there are totally 6 ways of picking up the cards right?
thats what is the definiton of possible cases. its possible to pick up any of the 6 cards right?

Read the question again.. and ...again
What is the probability that one of the cards was 5 if the sum of the two was 8?

hmm..
i still think that the problem is not well worded...

I found no ambiguity in the question.

ans is clearly 2/5
_________________

-----------------------------------------------------------
'It's not the ride, it's the rider'

Kudos [?]: 45 [0], given: 0

Re: card probability   [#permalink] 09 Sep 2008, 11:43
Display posts from previous: Sort by