BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

Trailing Zero

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Master | Next Rank: 500 Posts
Posts: 391
Joined: Sat Mar 02, 2013 5:13 am
Thanked: 50 times
Followed by:4 members

Trailing Zero

by rakeshd347 » Wed Oct 02, 2013 7:16 pm
Find the number of trailing zeros in the expansion of (20!*21!*22! ......... *33!)^3!.

A. 468
B. 469
C. 470
D. 467
E. 471

Is it GMAT like question?
Top
Source: — Problem Solving |
User avatar
Legendary Member
Posts: 1556
Joined: Tue Aug 14, 2012 11:18 pm
Thanked: 448 times
Followed by:34 members
GMAT Score:650

by theCodeToGMAT » Wed Oct 02, 2013 8:37 pm
20! to 24! ==> Each will give power of 4
25! to 29! ==> Each will give power of 6
30! to 33! ==> Each will give power of 7

So, 6(4*5 + 6*5 + 7*4) = 468

Answer [spoiler]{A}[/spoiler]
R A H U L
Top
User avatar
Master | Next Rank: 500 Posts
Posts: 283
Joined: Sun Jun 23, 2013 11:56 pm
Location: Bangalore, India
Thanked: 97 times
Followed by:26 members
GMAT Score:750

by ganeshrkamath » Wed Oct 02, 2013 11:31 pm
rakeshd347 wrote:Find the number of trailing zeros in the expansion of (20!*21!*22! ......... *33!)^3!.

A. 468
B. 469
C. 470
D. 467
E. 471

Is it GMAT like question?
The power of 3! = 6 indicates that the number of zeros = number of zeros in (20!*21!*...*33!) * 6
So search for an option that is a multiple of 6.
Choose A

Cheers
Every job is a self-portrait of the person who did it. Autograph your work with excellence.

Kelley School of Business (Class of 2016)
GMAT Score: 750 V40 Q51 AWA 5 IR 8
https://www.beatthegmat.com/first-attemp ... tml#688494
Top
Post new topic Post Reply
• Page 1 of 1