TrickyDS question

[dddanny2006]

Is mn divisible by 40?
(1)m is divisible by 40
(2)n is divisible by 4




Can anyone help me with this question via the Prime boxes method.

Thanks

[theCodeToGMAT]

dddanny2006, one question per thread please

[dddanny2006]

Done

dddanny2006, one question per thread please

[theCodeToGMAT]

To find: mn divisible by 40 ==> mn/4*2*5

So we need atleast single instance of "4", "2" & "5"

Statement 1:
m/40 ---> we got one instance of "4", "2" & "5"
Say m is 40
So, (40)(n)/40 ==> YES
But, "n" can be non-integer.
INSUFFICIENT

Statement 2:
n/4 --> we only got "4"
We don't know whether "m" is divisible by 10 or not.
Say n = 4, m = 15
(15)(4)/40 ==> NO
Say n = 4, m = 10
(4)(10)/40 ==> YES
INSUFFICIENT

Combining...
m/40 & n/4
We got "4", "2" & "5" also "n" is INTEGER.
SUFFICIENT

Answer [spoiler]{C}[/spoiler]

[dddanny2006]

I'd say statement 1 is insufficient because n may be an integer,say 0.5?

To find: mn divisible by 40 ==> mn/4*2*5

So we need atleast single instance of "4", "2" & "5"

Statement 1:
m/40 ---> we got one instance of "4", "2" & "5"
Say m is 40
So, (40)(n)/40 ==> YES
SUFFICIENT

Statement 2:
n/4 --> we only got "4"
We don't know whether "m" is divisible by 10 or not.
Say n = 4, m = 15
(15)(4)/40 ==> NO
Say n = 4, m = 10
(4)(10)/40 ==> YES
INSUFFICIENT

Is it Answer [spoiler]{A}[/spoiler]???

[dddanny2006]

I'd say statement 1 is insufficient because n could be an integer,say 0.5

To find: mn divisible by 40 ==> mn/4*2*5

So we need atleast single instance of "4", "2" & "5"

Statement 1:
m/40 ---> we got one instance of "4", "2" & "5"
Say m is 40
So, (40)(n)/40 ==> YES
SUFFICIENT

Statement 2:
n/4 --> we only got "4"
We don't know whether "m" is divisible by 10 or not.
Say n = 4, m = 15
(15)(4)/40 ==> NO
Say n = 4, m = 10
(4)(10)/40 ==> YES
INSUFFICIENT

Is it Answer [spoiler]{A}[/spoiler]???

[theCodeToGMAT]

yeah correct, I cannot assume that "n" is Integer; solution modified.