GMAT Prep / Number Properties

[Blast]

??

[Zipper]

1. When x is divided by 2, the remainder is 1 (so far we know that we'll always have a remainder); and when x is divided by 3, the reminder is 0.

this leaves us only with numbers with reminder 3.
(visualizing for better understanding though during the test this is not worth the time in most cases: 9/6=reminder3; 15/6=reminder3; 21/6=reminder3 etc.;
you can't have 6,12,18 since divided by 2 you should have reminder 1)

2. When x is divided by 12, the reminder is 3.

even easier to calculate, always reminder 3.

hence, D

[lunarpower]

this is also one of those problems where 'decoding' the statements by translating them into numbers works wonders: just sort through numbers by trial and error, and find the list of numbers that works for each statement.

(1)
the numbers that work for this statement are 3, 9, 15, 21, etc. adding 6 each time.

(2)
the numbers that work for this statement are 3, 15, 27, 39, etc. adding 12 each time.

if you make these lists - which hardly takes a prohibitive amount of time** - you'll find that either statement is sufficient on its own, so, (d).

incidentally, you should at least be able to translate '1 is the remainder upon dividing X by 2' into 'X is odd', IMMEDIATELY.

--

as i said here,
if you have a problem about REMAINDERS, you should view that problem as an opportunity for PATTERN RECOGNITION.
there are lots of topics that lead to recognition of common patterns - i.e., remainders aren't the only topic of such problems - but, in remainder problems, CLEAR patterns tend to emerge QUICKLY if you start testing numbers in some sort of systematic manner.

--

finally, i feel compelled to respond to the following:

visualizing for better understanding though during the test this is not worth the time in most cases:

kill that noise.

if you find a viable solution method, you should embark on it IMMEDIATELY, unless you KNOW it's going to take an absolutely ridiculous amount of time.
and you can rest assured that won't be the case here, because, as noted above, patterns on remainder problems tend to emerge early and often.

the last thing that you ever want to do on this test is sit there, staring dumbfounded at a problem, even though you have a potential solution method in mind. that will kill you.
if you think of a method involving plugging / listing, just start doing it. if it's going to be ridiculously time-consuming, you'll figure that out fast enough to abort it anyway - no harm done.
indecision is the WORST trait you can have on this test, bar none.

[Zipper]

I only mentioned it for better understanding for all other viewers (the OP of the thread and all other who might be interested in the answer). Just tried to do my best with the answer and not have posts after mine like "i still don't get it"; "can you explain it a a bit more" or something in those lines. I am at the beginning of my gmat preparation and I don't know 1/100 (probably even more) of the things you do. For instance I did not know that I could view reminders as an opportunity for pattern recognition. Hopefully, in my stay here I will pick up a lot of these tips/tricks to help me when I have to take the gmat. However I disagree with you in this particular case that I should "kill this noise". This "noise" in my opinion helps visualize the problems/answers and helps understanding what the guy was trying to say. I got to the answer without going trough this visualizations and with a lot of certainty I might add. I was so certain that I got it right (this doesn't mean I did, this means I was quite satisfied with the answer that I got, that I am sure that this visualization won't do anything but waste time for me). Of course it checks if the answer is right but if i start checking/rechecking everything that I am certain of.....

I see this is getting quite long and there is no point in that, coz all I am doing right now is wasting my time, wasting your time and the time of everybody that is going to read this post. I hope you understand what I meant. I didn't try to tell anybody "you don't have to visualize things on the GMAT test!", all I tried to say is "If you are quite certain of an answer in most cases It's a waste of time rechecking it". This is clearly my opinion and I am not trying to influence anybody with it. However, I do think this kind of "noise" helps a lot of people to better understand a certain solution and that's what it's all about.

[lunarpower]

I hope you understand what I meant. I didn't try to tell anybody "you don't have to visualize things on the GMAT test!", all I tried to say is "If you are quite certain of an answer in most cases It's a waste of time rechecking it".

ok, now i understand. i had actually taken your post to mean precisely what you hadn't meant it to: that "visualization" (in this case meaning "making lists of examples"), in most cases, is a waste of time.

it was the words "in most cases" that got me - especially because nowhere in your post did you mention anything about certainty or re-checking answers.

thanks for the clarification; we're on the same page.