Speed = 45 * 5/18 = 25/2 m/sec
Total distance covered = 360 + 140 = 750 m
Required time = 750 * 2/25 = 40 sec
A train 360 m long is running at a speed of 45 km/hr. In what time will it pass a bridge 390 m long?
Options:
(A) 40 sec
(B) 60 sec
(C) 45 sec
(D) 48 sec
(E) 50 sec
(B)

Speed = 50*(5/18) m/sec = 125/9 m/sec
Length of Train (Distance) = Speed * Time
(125/9) * 18 = 250 meter
A train running at the speed of 50 km/hr crosses a pole in 18 seconds. Find the length of the train.
Options:
(A) 150
(B) 188
(C) 250
(D) 288
(E) 300
(C)

A + B = 1/20 + 1/15 = 7/60
A + C = 1/20 + 1/12 = 8/60
7/60 + 8/60 = 15/60 = 1/4
4 days * 2 = 8 days

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
A can do a piece of work in 20 days. B in 15 days A and C in 12 days. In how many days can A finish the work if he is assisted by B on one day and C on the next, alternately?
Options:
(A) 9 days
(B) 8 days
(C) 5 days
(D) 54 days
(E) 2 days
(B)