What is the units digit of positive integer x?

Question

(1) 7, 15, 24, and n are all factors of x.
(2) 6! < x < 7!

Balajikarthick1990 · Answer

B is out straight away

A tells that number can end in 0/5

C is the answer i believe'

chetan2u · Answer

HI,
  Always be careful while eliminating a statement..  
what is statement I
(1) 7, 15, 24, and n are all factors of x.
the factors are 15 and 24, so x will be a MULTIPLE of 5 and 2..
thus UNIT's digit will be 0
Suff
ans A

Balajikarthick1990 · Answer

Ya agreed sir...will be careful.

stonecold · Answer

Since x is divisible by both 15 and 24 from statement 1 we can say that unit digit of x must be zero.
Again statement 2 is not sufficient as we don't know what x might be.
hence A

stonecold · Answer

Great Question.
Here we need the units digit of x
Statement 1=>
this statement tells us that 5 and 2 must be prime factors of x.
Hence the units digit of x must be zero.
Hence Sufficient.

Statement 2
x must lie between (720,720*7)
Not sufficient

Hence A

shameekv1989 · Answer

What is the units digit of positive integer x?

1) 7, 15, 24, and n are all factors of x

2) 6! < x < 7!

newyork2012 · Answer

1) with 15,24 ... the unit digit has to be 0
Sufficient 
1) from Too wide a range ... not sufficient

A

Posted from my mobile device

QuantMadeEasy · Answer

1) 7, 15, 24, and n are all factors of x
 Analysis: 
x is multiple of 7, 15, 24, and n

Simplify: 
x = 7*15*24*n
Unit digit of x = Product of unit digits of the given numbers = 7*5*4*n, which will be 0 as 5*4 is 20

Sufficient.

2) 6! < x < 7!
 Analysis: 
720<x<5040
Unit digit of x is unknown.
Insufficient

A is correct.

Concept: 
Unit digit of product of given numbers = Product of unit digits of the given numbers

Bunuel · Answer

Merging topics. Please check the discussion above. Hope it helps.

SChatrg · Answer

S1: Taking LCM(7,15,24,n) gives us that x is a multiple of 840n. Hence units digit is always 0. Sufficient.

S2: x lies between 6! and 7! - means multiple values. Insufficient.

Hence, option A.

bumpbot · Answer

Automated notice from GMAT Club BumpBot: 

A member just gave Kudos to this thread, showing it’s still useful. I’ve bumped it to the top so more people can benefit. Feel free to add your own questions or solutions.

 This post was generated automatically.

What is the units digit of positive integer x?

Prep Toolkit

Top 5 GMAT Debrief Videos

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards