Reasoning: 1/50 + 1/75 = 5/150
30/1 = 30 days
Ans: (A)
Question: Ravi can do a piece of work in 50 days while Prakash can do it in 75 days. In how many days will they finish it together?
Options:
(A) 30 days
(B) 35 days
(C) 25 days
(D) 27 days
(E) 29 days
Rationale: Six persons can be arranged in a row in 6! ways. Treat the three persons to sit together as one unit then there four persons and they can be arranged in 4! ways. Again three persons can be arranged among them selves in 3! ways. Favourable outcomes = 3!4! Required probability = 3!4!/6! = 1/5
The answer: (C)
Question: If six persons sit in a row, then the probability that three particular persons are always together is ?
Options:
(A) 1/6
(B) 1/0
(C) 1/5
(D) 1/4
(E) 1/1
Reasoning: Speed = 63 * 5/18 = 35/2 m/sec
Time taken = 70 * 2/35 = 16 sec
Ans: (A)
Question: A train 70 m long, running with a speed of 63 km/hr will pass a tree in?
Options:
(A) 4 sec
(B) 16 sec
(C) 6 sec
(D) 20 sec
(E) 8 sec
Rationale: 7 people can be prized with 5 distinct prizes in 7^5 ways
The answer: (C)
Question: In a race with 30 runners where 5 trophies will be given to the top 7 runners (the trophies are distinct: first place, second place, etc), how many ways can this be done?
Options:
(A) 8^8 ways
(B) 8^9 ways
(C) 7^5 ways
(D) 8^7 ways
(E) 8^6 ways
Reasoning: Answer = A. 20 miles
Relational speed = 110 - 100 = 10 miles per hour
In 6 hours, difference = 10 * 6 = 60 miles
Fast train trailing 40 miles, so effective difference = 60 - 40 = 20 miles
Ans: (A)
Question: Two trains are traveling on parallel tracks in the same direction. The faster train travels at 110 miles per hour, while the slower train travels at 100 miles per hour. At 1 o'clock the faster train is 40 miles behind the slower one. How far apart are the two trains at 7 o'clock?
Options:
(A) 20 miles
(B) 80 miles
(C) 90 miles
(D) 120 miles
(E) 400 miles
Reasoning: 2/7 * 6/7 * 1/3 * 1/8 = 1/98
Ans: (C)
Question: The compound ratio of 2/3, 6/7, 1/3 and 1/8 is given by?
Options:
(A) 7/98
(B) 1/48
(C) 1/98
(D) 1/96
(E) 1/68