DS question--modified from Ron's video

[dddanny2006]

Question source--Modified question --Ron Purewal video

Is m divisible by 8?
(1)mn is divisible by 8
(2)n is divisible by 8

Statement 2 is insufficient because n has nothing to do with m


Statement 1 says mn is divisible by 8. So in the prime box of mn we have a 2,2,2....?

For m to be divisible by 8 we need a 2,2,and 2. We dont know in statement 1 as to whether m or n has contributed to the 3 2's.

Therefore its insufficient.

I have doubts when combining the 2 statements.

mn primebox will have a 2,2,2...?

Statement 2 says n is divisible by 8 and thus the prime box of n will have a 2,2,2...?

Now were certain that the three 2's of the mn primebox are bought about by n from statement 2.Is it possible for the primebox of m to be empty or in other ways leaves the m primebox with just the dots and question mark like this "....?" only).Also answer the DS question via the same video method--Primebox .

Please clear this doubt Ron.

Thanks

Dan

[RonPurewal]

An "empty prime box" means that the number is 1. (This is easy to prove; just divide any number by itself.)

The problem here is that "divisible by 8" implies the presence of three or more 2's, not necessarily just three 2's. For instance, 64 = 2 x 2 x 2 x 2 x 2 x 2 is also divisible by 8.
If the prime box of mn has six or more 2's in it, then it will still be divisible by 8 even after you take out three of the 2's.

[RonPurewal]

It may be easier for you to come up with specific numbers that prove the statements insufficient, and then work out the prime boxes for those numbers. That way you'll be dealing with actual, concrete numbers, rather than annoyingly remote abstractions.

E.g., for "both statements together":
* If mn = 8 and n = 8, then m = 1, which is not divisible by 8.
* If mn = 64 and n = 8, then m = 8, which is divisible by 8.
So, (E).
These are relatively simple cases, so you should be able to see what's going on with the prime boxes.

[dddanny2006]

Ok ron..This is my method of solving the same,tell me if Im right.

Question source--Modified question --Ron Purewal video

Is m divisible by 8?
(1)mn is divisible by 8
(2)n is divisible by 8

Statement 2 is insufficient because n has nothing to do with m


Statement 1 says mn is divisible by 8. So in the prime box of mn we have a 2,2,2....?

For m to be divisible by 8 we need a 2,2,and 2. We dont know in statement 1 as to whether m or n has contributed to the 3 2's.

Therefore its insufficient.

I have doubts when combining the 2 statements.

mn primebox will have a 2,2,2...?

Statement 2 says n is divisible by 8 and thus the prime box of n will have a 2,2,2...?

Now were certain that the three 2's of the mn primebox are bought about by n from statement 2.Is it possible for the primebox of m to be empty or in other ways leaves the m primebox with just the dots and question mark like this "....?" only).Is it going to be empty or are the (...?)The answer is E right?



I have a doubt with the text in bold.Also have a look at the image that Ive attached here--

THe /img can attach my image

Here's the alternative
http://postimg.org/image/jd5ysrygz



Please clear this doubt Ron.

Thanks

An "empty prime box" means that the number is 1. (This is easy to prove; just divide any number by itself.)

The problem here is that "divisible by 8" implies the presence of three or more 2's, not necessarily just three 2's. For instance, 64 = 2 x 2 x 2 x 2 x 2 x 2 is also divisible by 8.
If the prime box of mn has six or more 2's in it, then it will still be divisible by 8 even after you take out three of the 2's.

[RonPurewal]

Please don't use the large size text; it's hard to read, and more than a bit annoying. Thanks. (Boldface is fine.)

The fact that you're left with nothing but dots indicates that nothing has to be in the prime box of "m". However, the dots indicate that anything still could be in that prime box -- anything at all.

If there's really nothing but dots, then m = 1.
If there are other factors still remaining after you take "n" out, then m is the product of those other factors.

Again, if this is not clear, then test specific numbers, and just see what happens to the boxes for those numbers.

[dddanny2006]

Sorry about that.Thanks for the explanation..

Ok ron..This is my method of solving the same,tell me if Im right.

Question source--Modified question --Ron Purewal video

Is m divisible by 8?
(1)mn is divisible by 8
(2)n is divisible by 8

Statement 2 is insufficient because n has nothing to do with m


Statement 1 says mn is divisible by 8. So in the prime box of mn we have a 2,2,2....?

For m to be divisible by 8 we need a 2,2,and 2. We dont know in statement 1 as to whether m or n has contributed to the 3 2's.

Therefore its insufficient.

I have doubts when combining the 2 statements.

mn primebox will have a 2,2,2...?

Statement 2 says n is divisible by 8 and thus the prime box of n will have a 2,2,2...?

Now were certain that the three 2's of the mn primebox are bought about by n from statement 2.Is it possible for the primebox of m to be empty or in other ways leaves the m primebox with just the dots and question mark like this "....?" only).Is it going to be empty or are the (...?)The answer is E right?



I have a doubt with the text in bold.Also have a look at the image that Ive attached here--

THe /img can attach my image

Here's the alternative
http://postimg.org/image/jd5ysrygz



Please clear this doubt Ron.

Thanks

An "empty prime box" means that the number is 1. (This is easy to prove; just divide any number by itself.)

The problem here is that "divisible by 8" implies the presence of three or more 2's, not necessarily just three 2's. For instance, 64 = 2 x 2 x 2 x 2 x 2 x 2 is also divisible by 8.
If the prime box of mn has six or more 2's in it, then it will still be divisible by 8 even after you take out three of the 2's.

[RonPurewal]

Sure. No worries.