![]() |
| PS-#33 (Number Properties) |
|
Stacey Koprince
MGMAT STAFF
|
Several words are important here.
First, if an integer is divisible by certain other integers, those other integers are factors of the main integer in question, and I can create the integer in question by multiplying those factors. So if I want an integer (but not necessarily the smallest) that is divisible by 1 thru 7 inclusive, I need something that has all the necessary components as factors. That means I need to multiply: 1*2*3*4*5*6*7. The question also says, though, that it wants the LOWEST integer that fits the criteria, not just any integer. So I want to use the minimum necessary when figuring out what to multiply: 1 2 (have I included a 2 yet? No, so keep this one in) 3 (have I included a 3 yet? No, so keep this one in) 4, or 2*2 (have I included any 2's yet? Yes, I've included one from above. How many more do I need to make a 4? Just one more 2. So add in only one 2 here, not two 2's) 5 (have I included a 5 yet? No, so keep this one in) 6, or 2*3 (have I included any 2's or 3's yet? Yes, I've got a 2 up above and a 3 up above, so I've already created my 6. I don't need to include anything more here) 7 (have I included a 7 yet? No, so keep this one in) That leaves me with: 1*2*3*2*5*7. (And, of course, you can ignore the 1, since it won't change the answer.) |
||||||||||||
|
|
|||||||||||||
|
Guest
|
Is there a quicker way to do that? After reading the question text should you recognize this is an LCM question?
|
||||||||||||
|
|
|||||||||||||
|
Stacey Koprince
MGMAT STAFF
|
Yes, I was laying it out for you step by step to make sure you understood - the culmination is that it is an LCM problem. So you wouldn't go through the first set of things I wrote down. You'd just recognize that you want the minimum necessary, based on the words "lowest" and "integer that is divisible by" and write down: 2*3*2*5*7 (asking yourself that series of questions I typed for each number).
|
||||||||||||
|
|
|||||||||||||
|
Guest
|
Thank you Stacey. Your explanation for LCM helped me understand the concept a little better.
|
||||||||||||
|
|
|||||||||||||
|
Stacey Koprince
MGMAT STAFF
|
Great!
|
||||||||||||
|
|
|||||||||||||
| PS-#33 (Number Properties) |
|
||
|
Powered by phpBB © phpBB Group
Content © Manhattan GMAT Forums
*GMAT and GMAT CAT are registered trademarks of the Graduate Management Admission Council,
which neither sponsors nor endorses this test preparation service.
Content © Manhattan GMAT Forums
*GMAT and GMAT CAT are registered trademarks of the Graduate Management Admission Council,
which neither sponsors nor endorses this test preparation service.


