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

 It is currently 23 Aug 2016, 18:39

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

If d is a positive integer and f is the product of the first

Author Message
TAGS:

Hide Tags

Manager
Joined: 27 May 2010
Posts: 102
Followers: 2

Kudos [?]: 6 [0], given: 13

Re: DS : product of first 30 positive integers [#permalink]

Show Tags

14 Aug 2010, 09:06
thanks for the tip on trailing zeroes bunuel.
Intern
Status: "You never fail until you stop trying." ~Albert Einstein~
Joined: 16 May 2010
Posts: 31
Followers: 0

Kudos [?]: 4 [0], given: 7

Re: DS : product of first 30 positive integers [#permalink]

Show Tags

12 Jan 2011, 23:42
awesome bunuel. Trailing Zero is a very interesting concept that will be helpful =)
Intern
Joined: 30 Mar 2011
Posts: 20
Followers: 0

Kudos [?]: 4 [0], given: 0

Number properties question - factorials [#permalink]

Show Tags

30 Apr 2011, 23:50
Question:

If d is a positive integer and f is the product of the first 30 positive integers, what is the value of d?

(1) 10^(d) is a factor of f
(2) d > 6
Math Forum Moderator
Joined: 20 Dec 2010
Posts: 2021
Followers: 157

Kudos [?]: 1556 [0], given: 376

Re: Number properties question - factorials [#permalink]

Show Tags

01 May 2011, 00:01
chloeholding wrote:
Question:

If d is a positive integer and f is the product of the first 30 positive integers, what is the value of d?

(1) 10^(d) is a factor of f
(2) d > 6

gmatprep-ds-product-of-first-30-integers-87454.html

 ! Please post PS questions in the PS sub-forum: gmat-problem-solving-ps-140/Please post DS questions in the DS sub-forum: gmat-data-sufficiency-ds-141/No posting of PS/DS questions is allowed in the main Math forum.

_________________
Intern
Joined: 07 Jan 2011
Posts: 25
Followers: 1

Kudos [?]: 2 [0], given: 1

Re: Number Properties from GMATPrep [#permalink]

Show Tags

12 Sep 2011, 06:22
Thanks for this explanation Bunuel.
Intern
Joined: 03 Jan 2011
Posts: 21
Followers: 0

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

Re: DS: GMAT Prep - What is the value of d? [#permalink]

Show Tags

13 Sep 2011, 08:27
A nice question, here is my approach.

F=1*2*3......*30
Now F would have Seven 5's.

Thus from 10^1 till 10^7 is possible.
a. A doesnt help in reducing this.
b. Useless all alone.

Combining both we get that the value has to be 10^7.

And thus the answer is C.
Manager
Status: MBA Aspirant
Joined: 12 Jun 2010
Posts: 178
Location: India
WE: Information Technology (Investment Banking)
Followers: 3

Kudos [?]: 67 [0], given: 1

Show Tags

17 Sep 2011, 06:12
richardj wrote:
The maximum value of d = int(d/5) + int (d/(5^2)) + ....

d = int(30/5) + int(30/25) + ... = 6 + 1 + 0 = 7

Manager
Status: Retaking next month
Affiliations: None
Joined: 05 Mar 2011
Posts: 229
Location: India
Concentration: Marketing, Entrepreneurship
GMAT 1: 570 Q42 V27
GPA: 3.01
WE: Sales (Manufacturing)
Followers: 5

Kudos [?]: 85 [0], given: 42

Re: DS: GMAT Prep - What is the value of d? [#permalink]

Show Tags

18 Sep 2011, 21:52
Clear C it is.

The key to this problems is to look for no of 5's in the given product.
Director
Joined: 03 May 2007
Posts: 886
Schools: University of Chicago, Wharton School
Followers: 6

Kudos [?]: 140 [0], given: 7

Re: DS: GMAT Prep - What is the value of d? [#permalink]

Show Tags

23 Sep 2011, 17:00
zoom wrote:
If $$d$$ is a positive integer and $$f$$ is the product of the first $$30$$ positive integers, what is the value of $$d$$?

1) $$10^d$$ is a factor of $$f$$
2) $$d > 6$$

Image:
Attachment:
GPrep_d_is_a_positive_integer.png

d = 30!
f = a positive integer

1) f = k(10^d) where k is an integer
30! = k (10^d)

Since d is a positive integer, how many 10s are in 30!?

30/5 = 6
30/25 = 1

so there are seven 10s in 30! and d could be 0, 1, .......7. NSF.

2) d > 6,m so what ? nothing because we do not know the relationship between d and f. NSF..

1 & 2) Oh yeah... now we has relationship between d and f. Also we know the exact value of d i.e. 7.

Sufficient.. D = 7.

Then it is C.
Manager
Status: Target MBA
Joined: 20 Jul 2010
Posts: 211
Location: Singapore
Followers: 0

Kudos [?]: 15 [0], given: 12

Re: DS: GMAT Prep - What is the value of d? [#permalink]

Show Tags

29 Sep 2011, 07:15
zoom wrote:
If $$d$$ is a positive integer and $$f$$ is the product of the first $$30$$ positive integers, what is the value of $$d$$?

1) $$10^d$$ is a factor of $$f$$
2) $$d > 6$$

Image:
Attachment:
GPrep_d_is_a_positive_integer.png

d = +ve
f = 30!
Q: d=?

1)
max. powers of 10 in 30!
int(30/5) + int(30/25) = 7
but, does not tell value of d
0 <= d <= 7
Insufficient

2) Insufficient

3) Combining
0 <= d <= 7 ===> from (1)
d > 6 ===> from (2)
we get d =7
Sufficient, hence (C)
_________________

Thanks and Regards,
GM.

Re: DS: GMAT Prep - What is the value of d?   [#permalink] 29 Sep 2011, 07:15

Go to page   Previous    1   2   3   4   [ 70 posts ]

Similar topics Replies Last post
Similar
Topics:
1 A, B, C, D, E, and F are six consecutive positive odd integers in 2 25 Apr 2016, 15:10
3 If d is a positive integer, is d^1/2 an integer? 5 26 Feb 2014, 02:26
3 If c and d are positive, is d an integer ? 3 22 Jul 2012, 18:17
80 If d is a positive integer and f is the product of the first 22 28 Jan 2012, 18:13
6 If d is a positive integer, is d^1/2 an integer ? 7 15 Feb 2011, 11:53
Display posts from previous: Sort by