IMHO A we know, that 3^1=3(9 is a unit digit) 3^2=9(9 is a unit digit) 3^3=27 (7 is a unit digit) 3^4=81 (1 is a unit digit) 3^5=243(3 is a unit digit) so , now we r moving to stmnt 1 x+y=7 since we know that x and y are positive integers, then x colud be equal to 3;5;4;2 ,then y will be equal to 4...

Whoever wrote this question obviously did not study for the verbal portion of the GMAT.

I got it right with a lucky guess.

I knew it wasn't 2/3 because the selection pool isn't the same as the number in the chosen group (12, 15) and E seemed too close to absolute certainty.

1/5 is equal to 0 with remainder of 1?

"1/5 is equal to 0 with remainder of 1."

This statement was made in GMAT Data Sufficiency Lesson 8. How is this even possible?

I fell for the trap answer C.

Can it be fair to say that every time we are given a time problem and solve for the rate, all we have to do is take the inverse?

1) is 1/3 or 33%.

2) is < 33%

That kills B C E and D.

It's E because you know the males who are custodial staff from 1) and females who are custodial staff from 2). There are still two holes to fill: males who aren't custodial staff and females who aren't custodial staff.

I think it's E.

xy raised to 2z will mask the sign of xy since it's positive no matter what.

We also don't know if z is positive or negative.