Working alone, Printers X, Y, and Z can do a certain printing job, consisting of a large number of pages, in 12, 25, and 30 hours, respectively. What is the ratio of the time it takes Printer X to do the job, working alone at its rate, to the time it takes Printers Y and Z to do the job, working together at their individual rates?
Options:
(A) 4/11
(B) 1/2
(C) 15/22
(D) 150/11
(E) 11/4

P1 takes 12 hrs
Rate for P2P3 together = 1/25 + 1/30 = 11/150
Therefore they take 150/11
Ratio = 150/11 = So the answer is: (D).

A man rows his boat 90 km downstream and 5' km upstream, taking 3 hours each time. Find the speed of the stream?
Options:
(A) 7 kmph
(B) 5 kmph
(C) 2 kmph
(D) 8 kmph
(E) 1 kmph

Speed downstream = d/t = 90/(3) = 30 kmph
Speed upstream = d/t = 51/(3) = 17 kmph
The speed of the stream = (30 - 17)/2 = 7 kmph So the answer is: (A).

A can do a job in 18 days and B can do it in 30 days. A and B working together will finish twice the amount of work in ------- days?
Options:
(A) 21 days
(B) 22 days
(C) 23 days
(D) 12 days
(E) none of these

1/18 + 1/30 = 8/90 = 4/45
45/4 = 11 *2 = 22 days So the answer is: (B).

What is the probability of rolling a nine with two, fair, six-sided dice?
Options:
(A) 1/6
(B) 1/9
(C) 2/13
(D) 1/12
(E) 5/36
There are 4 ways to roll a nine: 3 and 6, 6 and 3, 4 and 5, 5 and 4 with two six-sided dice. There are 6 times 6 = 36 ways to roll two dice. The probability of rolling a 9 is thus 4/36 = 1/9. So the answer is: (B).