ivsham

This is an older thread: http://www.www.urch.com/forums/gre-math/65103-qc-bugged-me-couple-hours.html

Given the figure ABCD is a rectangular, the answer CANNOT be C, I also opt for B.

Goldust, thanks for the correction... I see, I ignored the bell-shape of the normal distribution... By the way, what is the OA? This question appears in the Powerprep 3.1 tutorial and has a rather unclear explanation.

...my explanation: I would chose answer d 70, simply because: 1/ it is half way b/n 55 and 85 2/ it's value is half way b/n 450 and 650. 3/ the inflection points that DWarrior mentions in the post above have already occured i.e. no change in graph's direction is expected in the searched for zone. this is my simple logic...correct me if I'm wrong :hmm: I don't expect ETS to with any complicate calculations in 2 minutes :)

I found this older very similar post, look at question #2: http://www.www.urch.com/forums/gre-math/78983-normal-distribution-q.html

Logic: Bigger rectangle/smaller => you get answer C

They ask you: which number multiplied by (1,21=1,1*1,1) gives 726. Ans 600.

Not enough info -> answer D

It seems that the solutions proposed are for problems, which text is missing. Could someone post them again? Thanks!

I also receive 50 %: we have two independent events with probability of 1/2 and two repetitions.

I get the same answer!

I see - we asume the velocity of A&B to be the same as A and B separately. Thanks.

For problem 1: I agree that 2,5 gallons remain after A stops working, but how are you sure that A&B complete the job for exactly 1 minute???

Thank you, Skawal! I still have doubts about the second problem, I 've seen a similar situation in which from the total # combinations is substracted the number of that items we do not want, so that "at least condition holds" but here i don't know how to express the red and white balls.

1/ A test comprises two parts (A, B), each with 5 questions. If a candidate must solve 6 problems but is not permitted to attempt to solve more than 4 problems from each of the two parts, then in how many ways can he select the questions? Answer (not confirmed) 200 2/ A box contains 2 white balls, 3 black balls and 4 red. In how many ways can 3 balls be drawn, if at least one MUST be black. Answer (not confirmed) 64. 3/ A reflection of a positive integer is obtained by reversing its digits. Example of ETS: 321 and 123. The difference of a five digit integer and its reflection MUST be divisible by:2,4, 5, 6, 9 OA: 9 I receive by the try and error method that as a general rule then number is divisible by 2,4,6,9 and a weird numbers like this give the OA: 45008-80045=-35037, 8009-9008=999 Do you have a more stightforward idea how to approach it?