Problem from probability!

[swapy_shine]

Please help in solving this question!!!..thanks

The only content of a container are 10 ball that are each numbered with a different positive integer from 1 through 10, inclusive. If 4 balls are to be selected one after the other, with each ball selected at random and without replacement, what is the probability that the range of the numbers on the balls selected is 7?
a)1/2
b) 5/15
c) 3/14....@@@
d) 15/28
e) 3/7

[tommywallach]

Hey Swapy,

This is not a realistic GRE question. It's far too hard for the GRE. It's actually been posted on this forum before, if I remember correctly. But I don't like answering these, because it makes it seem like you have to be able to do this to do the GRE...which you don't!

-t

[swapy_shine]

Hi Tommy,
I got this questions on one of the online practice test website. Anyways good to know that this level is not usually seen in real GRE!!!

Thanks

[tommywallach]

Yeah, there are a LOT of really bad companies out there. I'd recommend you stick with the big names. Not just us, but Kaplan, Princeton Review, Magoosh--those types of folks.

-t