Last visit was: 23 Jul 2024, 14:37 It is currently 23 Jul 2024, 14:37
Toolkit
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
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

# What is the units digit of the product of the first 50 primes?

SORT BY:
Tags:
Show Tags
Hide Tags
Intern
Joined: 04 Mar 2010
Posts: 6
Own Kudos [?]: 29 [11]
Given Kudos: 1
Intern
Joined: 10 Feb 2013
Posts: 14
Own Kudos [?]: 24 [6]
Given Kudos: 6
Location: India
Concentration: General Management, Finance
GMAT Date: 05-16-2015
GPA: 3.67
WE:Programming (Computer Software)
General Discussion
SVP
Joined: 27 Dec 2012
Status:The Best Or Nothing
Posts: 1558
Own Kudos [?]: 7303 [4]
Given Kudos: 193
Location: India
Concentration: General Management, Technology
WE:Information Technology (Computer Software)
Senior Manager
Joined: 07 Aug 2011
Posts: 422
Own Kudos [?]: 1798 [0]
Given Kudos: 75
GMAT 1: 630 Q49 V27
Re: What is the units digit of the product of the first 50 primes? [#permalink]
PareshGmat wrote:

Just write down the first 4 prime numbers & we get the answer

1*2*3*5 ............ and so on... will end up with 0 in units place

Similar question......

What is the units digit of the product of the first 100 even numbers?

2*4*6*8*10 ............. will end up in 0 in the units place

What is the units digit of the product of the first 100 odd numbers?

1*3*5*7 ................... will end up in 5 in the units place

Experts: Are these potential GMAT questions.... ??

Prime starts from 2 not from 1 .. . . .
GMAT Club Legend
Joined: 19 Dec 2014
Status:GMAT Assassin/Co-Founder
Affiliations: EMPOWERgmat
Posts: 21835
Own Kudos [?]: 11795 [2]
Given Kudos: 450
Location: United States (CA)
GMAT 1: 800 Q51 V49
GRE 1: Q170 V170
Re: What is the units digit of the product of the first 50 primes? [#permalink]
2
Kudos
Hi All,

On Test Day, sometimes the biggest clue/shortcut will be in how the answer choices are written.

We're asked to think about the PRODUCT of the first 50 prime numbers. We clearly are NOT expected to do all of that math, so there MUST be a pattern that we can use to get to the correct answer.

Since the first prime is "2", the product of all of those primes MUST be EVEN. Considering how THESE answers are written, only one answer matches...

GMAT assassins aren't born, they're made,
Rich
Senior Manager
Joined: 23 Jan 2013
Posts: 424
Own Kudos [?]: 268 [0]
Given Kudos: 43
Schools: Cambridge'16
Re: What is the units digit of the product of the first 50 primes? [#permalink]
no need to count. All primes are odd and multiplying by 2 (only even prime) we get even

Only A fits
Manager
Joined: 25 Mar 2013
Posts: 166
Own Kudos [?]: 133 [0]
Given Kudos: 101
Location: United States
Concentration: Entrepreneurship, Marketing
GPA: 3.5
Re: What is the units digit of the product of the first 50 primes? [#permalink]
Product of 50 primes
2 , 3 , 5 , 7 ...
2x5 = 10
A
Director
Joined: 02 Sep 2016
Posts: 525
Own Kudos [?]: 195 [0]
Given Kudos: 277
Re: What is the units digit of the product of the first 50 primes? [#permalink]
That can be one way to solve: 2*5=10
So no matter what the other nos. are the answer will end with 0 at unit's place.

I solved it using the power of even numbers.

Even is there is one even no. in the list, then the product will be even and luckily 2 is part of the list.
Only even choice is 0.
Non-Human User
Joined: 09 Sep 2013
Posts: 34049
Own Kudos [?]: 853 [0]
Given Kudos: 0
Re: What is the units digit of the product of the first 50 primes? [#permalink]
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
Re: What is the units digit of the product of the first 50 primes? [#permalink]
Moderator:
Math Expert
94589 posts