GMATPrep Practice Test 1 - Help with DS question

I think this question is a classic in this forum...the problem is that the official answer undestands that each tool both is separated from the next one evenly...

...I personally dont agree with the OA because I think that its supposing a lot... but still... :D

cris wrote:I think this question is a classic in this forum...the problem is that the official answer undestands that each tool both is separated from the next one evenly...

...I personally dont agree with the OA because I think that its supposing a lot... but still...

U said a lot about OA but what's the OA, man? IMO C. But let me know about the OA ...

rainbownlife wrote:please explain:

On her way home from work janet drives thru several toolbooths.Is there a pair of these toolbooths that are < 10 miles?

(1) first and last booths are 25 miles apart.

(2) janet drives thru 4 tool booths.

(1) by itself is insufficient, since there could be only 2 booths or there could be lots of booths. Maybe yes, maybe no.

(2) by itself is insufficient because we have no clue what the spacing is like.

However, if we know that there are 4 booths and the distance from booth 1 to booth 4 is 25 miles, we know that at least 2 of the booths have to be within 10 miles of each other. We do NOT need to assume even spacing.

With 4 booths, we have 3 "gaps" (i.e. from 1 to 2, 2 to 3 and 3 to 4).

25/3 = an average of 8 1/3 miles per gap. To get an average of 8 1/3, at least one of the gaps has to be 8 1/3 miles or less (if all 3 gaps were greater than 8 1/3, then the average would be greater than 8 1/3).

So, for example, the gaps could be 3 * 8 1/3; or the gaps could be 12, 12 and 1; or the gaps could be 1, 1 and 23; or an infinite number of other possibilies, but in EVERY case at least one of the gaps is less than or equal to 8 1/3 miles. Together the statements give us a definite yes: choose (c).

I got stuck on this one, too. I had read it 'greater than' rather than 'less than' though, and really tripped myself up. A great lesson for me in reading the questions carefully! Best wishes!

thanks guys for all your responses!