It is currently 19 Oct 2017, 13:07

### 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

# Larry tried to type his new 7-digit phone number on a form,

Author Message
SVP
Joined: 21 Jul 2006
Posts: 1512

Kudos [?]: 1006 [0], given: 1

Larry tried to type his new 7-digit phone number on a form, [#permalink]

### Show Tags

05 Aug 2008, 11:46
00:00

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 0 sessions

### HideShow timer Statistics

This topic is locked. If you want to discuss this question please re-post it in the respective forum.

Larry tried to type his new 7-digit phone number on a form, but what appeared on the form was 39269, since the '4' key on his computer no longer works. His secretary has decided to make a list of all of the numbers that could be Larry's new number. How many numbers will there be on the list?

a) 21
b) 24
c) 25
d) 30
e) 36

thanks

Kudos [?]: 1006 [0], given: 1

SVP
Joined: 30 Apr 2008
Posts: 1867

Kudos [?]: 615 [0], given: 32

Location: Oklahoma City
Schools: Hard Knocks

### Show Tags

05 Aug 2008, 11:56
i think A.

Essentially we have 7 options. We need to find out how many different variations there are for 2 of those numbers. That seems like it would be $$C_7^2 = 21$$.

tarek99 wrote:
Larry tried to type his new 7-digit phone number on a form, but what appeared on the form was 39269, since the '4' key on his computer no longer works. His secretary has decided to make a list of all of the numbers that could be Larry's new number. How many numbers will there be on the list?

a) 21
b) 24
c) 25
d) 30
e) 36

thanks

_________________

------------------------------------
J Allen Morris
**I'm pretty sure I'm right, but then again, I'm just a guy with his head up his a.

GMAT Club Premium Membership - big benefits and savings

Kudos [?]: 615 [0], given: 32

Intern
Joined: 04 Jun 2008
Posts: 16

Kudos [?]: 13 [0], given: 0

Concentration: Marketing, Strategy
GMAT 1: 690 Q48 V35
GPA: 3.31
WE: Engineering (Non-Profit and Government)

### Show Tags

05 Aug 2008, 12:03
tarek99 wrote:
Larry tried to type his new 7-digit phone number on a form, but what appeared on the form was 39269, since the '4' key on his computer no longer works. His secretary has decided to make a list of all of the numbers that could be Larry's new number. How many numbers will there be on the list?

a) 21
b) 24
c) 25
d) 30
e) 36

thanks

7 options and 2 different instances of 4:

C(7,2) = 21

Longer way:

44.....
4.4....
4..4...
4...4..
4....4.
4.....4
.44....
.4.4...
.4..4..
.4...4.
.4....4
..44...
..4.4..
..4..4.
..4...4
...44..
...4.4.
...4..4
....44.
....4.4
.....44

=21

A

Kudos [?]: 13 [0], given: 0

Senior Manager
Joined: 23 May 2006
Posts: 322

Kudos [?]: 386 [0], given: 0

### Show Tags

05 Aug 2008, 12:04
Larry's typed the seven digits, however since only (39269) five digits appeared the rest fo the two digits must be two 4's.
Now I think if we can rephrase the question by saying - how many ways can we arrange two numbres in seven slots.

7c2 = 21.

Not sure if this is the right answer.

IMO A

Kudos [?]: 386 [0], given: 0

SVP
Joined: 21 Jul 2006
Posts: 1512

Kudos [?]: 1006 [0], given: 1

### Show Tags

05 Aug 2008, 12:29
thanks guys. OA is A

Kudos [?]: 1006 [0], given: 1

SVP
Joined: 07 Nov 2007
Posts: 1792

Kudos [?]: 1060 [0], given: 5

Location: New York

### Show Tags

05 Aug 2008, 12:37
tarek99 wrote:
Larry tried to type his new 7-digit phone number on a form, but what appeared on the form was 39269, since the '4' key on his computer no longer works. His secretary has decided to make a list of all of the numbers that could be Larry's new number. How many numbers will there be on the list?

a) 21
b) 24
c) 25
d) 30
e) 36

thanks

7C2 = 7 options chose 2 places =
21.
_________________

Smiling wins more friends than frowning

Kudos [?]: 1060 [0], given: 5

VP
Joined: 17 Jun 2008
Posts: 1374

Kudos [?]: 406 [0], given: 0

### Show Tags

05 Aug 2008, 17:31
tarek99 wrote:
Larry tried to type his new 7-digit phone number on a form, but what appeared on the form was 39269, since the '4' key on his computer no longer works. His secretary has decided to make a list of all of the numbers that could be Larry's new number. How many numbers will there be on the list?

a) 21
b) 24
c) 25
d) 30
e) 36

thanks

Number of ways to put a single number in 5 digits(different from the number) is 6.Now consider this 6 digit number hence formed and here to append one number same as previous is 6 again excluding the possibility off two same numbers together two times.
hence 6*6=36 combinations are possible.

_________________

cheers
Its Now Or Never

Kudos [?]: 406 [0], given: 0

VP
Joined: 17 Jun 2008
Posts: 1374

Kudos [?]: 406 [0], given: 0

### Show Tags

05 Aug 2008, 17:34
spriya wrote:
tarek99 wrote:
Larry tried to type his new 7-digit phone number on a form, but what appeared on the form was 39269, since the '4' key on his computer no longer works. His secretary has decided to make a list of all of the numbers that could be Larry's new number. How many numbers will there be on the list?

a) 21
b) 24
c) 25
d) 30
e) 36

thanks

Number of ways to put a single number in 5 digits(different from the number) is 6.Now consider this 6 digit number hence formed and here to append one number same as previous is 6 again excluding the possibility off two same numbers together two times.
hence 6*6=36 combinations are possible.

mistake
2C7 is better i overlooked the conditions common between all.
_________________

cheers
Its Now Or Never

Kudos [?]: 406 [0], given: 0

Re: PS: Interesting problem   [#permalink] 05 Aug 2008, 17:34
Display posts from previous: Sort by