Sum of 10 even numbers = 10 * 11 = 110
Average = 110/10 = 11
The average of first 10 even numbers is?
Options:
(A) 19
(B) 18
(C) 16
(D) 11
(E) 17
(D)

P1 takes 12 hrs
Rate for P2P3 together = 1/25 + 1/30 = 11/150
Therefore they take 150/11
Ratio = 150/11 =
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
(D)

S = (500 + 300)/45 = 800/45 * 18/5 = 64

A train 500 meters long completely crosses a 300 meters long bridge in 45 seconds. What is the speed of the train is?
Options:
(A) 32
(B) 28
(C) 49
(D) 64
(E) 21
(D)