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

Redeem

number properties question - logically working through a qu.

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Master | Next Rank: 500 Posts
Posts: 203
Joined: Wed Jun 04, 2008 1:01 am
Location: Windsor
Thanked: 5 times
GMAT Score:650

number properties question - logically working through a qu.

by jsl » Fri Jul 11, 2008 6:51 am
How do you guys work through this question logically so that you can come to a definitive answer within 2 mins? I'm struggling as I keep confusing concepts...

What is the remainder when the positive integer x is divided by 4?

1. There is no remainder when 2x is divided by 4.
2. There is no remainder when x/2 is divided by 4.
Top
Source: — Data Sufficiency |
User avatar
Master | Next Rank: 500 Posts
Posts: 246
Joined: Mon May 19, 2008 7:34 am
Location: Texaco Gas Station
Thanked: 7 times

by cubicle_bound_misfit » Fri Jul 11, 2008 7:49 am
Let's try it

stmt1 says

2x%4 =0
==> 2x = 4k where k>0 k belongs to I

for k=1 x=2 ==> 2%4 =2 , for k=2 x=4==> 4%4 =0 not sufficient.

stmt 2 says

x/2%4=0
==> x/2 = 4k where k>0 k belongs to I

x = 8k for any value of k x%4 =0 Sufficient.

Answer B.
Please let me know OA.

Regards,
Cubicle Bound Misfit
Top
Senior | Next Rank: 100 Posts
Posts: 31
Joined: Thu Jul 10, 2008 9:02 pm
Thanked: 1 times

by tzink » Fri Jul 11, 2008 8:23 am
Just jumping in this thread, but I didn't follow that explanation..
First, what's up with the percentage signs? I assume you mean division...
Also, what do you mean "K belongs to I"?
Where does the K come from/what does it mean?

Sorry noob questions...
Top
User avatar
Master | Next Rank: 500 Posts
Posts: 246
Joined: Mon May 19, 2008 7:34 am
Location: Texaco Gas Station
Thanked: 7 times

by cubicle_bound_misfit » Fri Jul 11, 2008 9:04 am
K belongs to set of all Integers

% = modulus operation i.e. 5%2 = remainder of 5 divided by 2


regards,
Cubicle Bound Misfit
Top
Junior | Next Rank: 30 Posts
Posts: 24
Joined: Sun May 04, 2008 12:18 pm
Thanked: 1 times

by target790 » Fri Jul 11, 2008 9:27 am
(1)
2x/4 leaves no remainder where x={1,2....9}

In this scenario x can be 2,4,6 or 8

Not sufficient as there are multiple remainder options in this case.

(2)

x/8 leaves no remainder where x={1,2...9}

Only possible when x=8

So this option is sufficient.


Option B
Top
Master | Next Rank: 500 Posts
Posts: 203
Joined: Wed Jun 04, 2008 1:01 am
Location: Windsor
Thanked: 5 times
GMAT Score:650

by jsl » Fri Jul 11, 2008 12:11 pm
Official Answer is B
Top
Master | Next Rank: 500 Posts
Posts: 203
Joined: Wed Jun 04, 2008 1:01 am
Location: Windsor
Thanked: 5 times
GMAT Score:650

by jsl » Fri Jul 11, 2008 12:15 pm
target790 wrote:x/8 leaves no remainder where x={1,2...9}
Thanks for this part.... can you explain why you only tested integers from 1 to 9 inclusive? Is this a general rule I can apply to all integer testing questions such as this?
Top
Junior | Next Rank: 30 Posts
Posts: 24
Joined: Sun May 04, 2008 12:18 pm
Thanked: 1 times

by target790 » Fri Jul 11, 2008 2:36 pm
against this problem you can easily generalize.

Let me elaborate a bit more.


statement 1>x/2 where x can be any positive integer.So x should be multiples of 2(2,4,6,8.....)
In these even set you can't manage specific remainder when you divide by 4.

So this is not sufficient.


statement2>x/8 where x is any positive integers.
Now if x leaves no remainder when you divide by 8 the you can conclude easily that division by 4 will also not leave any remainder.

So this is sufficient.


Answer is B



Hope,it's now much more clear
Top
Post new topic Post Reply
• Page 1 of 1