It is currently 12 Dec 2017, 17:58

### 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

# m12 Q 25

Author Message
Intern
Status: GMAT once done, Going for GMAT 2nd time.
Joined: 29 Mar 2010
Posts: 34

Kudos [?]: 9 [0], given: 3

Location: Los Angeles, CA
Schools: Anderson, Haas, Ross, Kellog, Booth, McCombs

### Show Tags

05 Jun 2011, 19:01
What is 1! + 2! + ... + 10!?

* 4,037,910
* 4,037,913
* 4,037,915
* 4,037,916
* 4,037,918

What is the easy way to solve this question? Thanks in advance.
_________________

BP

Kudos [?]: 9 [0], given: 3

Senior Manager
Joined: 24 Mar 2011
Posts: 428

Kudos [?]: 223 [0], given: 20

Location: Texas

### Show Tags

05 Jun 2011, 20:24
I won't solve it, but thinking it logically to choose the correct answer.

you know that there is 1! so final addition has to be odd.
So you can knock out 1st, 4th and 5th option.

Now there is little process to pick one of the 2nd or 3rd.

excluding 1! you have, 2!+3!+.....+9!+10!
to pick one choice some of these numbers has to be either 4037912 or 4037914
now see the number of 2's in above series..

2 + 2^1 *3 + 2^3*3 + 2^3 *3*5 + ....

= 2(1 + 3 + 2^2*3 + ..)

if you divide above numbers by 2 both are divisible, so you need to go further -

= 2(4 + 2^2 * 3 +... )
= 2*2^2 (1 + 3 +..)
now if you notice 4037912 is divided by 8 but not 4037917.

Kudos [?]: 223 [0], given: 20

Math Forum Moderator
Joined: 20 Dec 2010
Posts: 1949

Kudos [?]: 2135 [2], given: 376

### Show Tags

06 Jun 2011, 01:36
2
KUDOS
valencia wrote:
What is 1! + 2! + ... + 10!?

* 4,037,910
* 4,037,913
* 4,037,915
* 4,037,916
* 4,037,918

What is the easy way to solve this question? Thanks in advance.

Unit's digit of 1!+2!+3!+4!=3
Unit's digit of the sum of the remaining integers will always be 0 i.e. 5!+6!+.....+$$\infty !$$=0
Thus, the unit's digit of the above summation=3+0=3
Only B fits.

Ans: "B"
_________________

Kudos [?]: 2135 [2], given: 376

Re: m12 Q 25   [#permalink] 06 Jun 2011, 01:36
Display posts from previous: Sort by

# m12 Q 25

Moderator: Bunuel

 Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.