Rationale: 1/14 - 1/28 = 1/28
28 minutes
The answer: (C)
Question: A pipe can fill a cistern in 14 minutes whereas the cistern when fill can be emptied by a leak in 28 minutes. When both pipes are opened, find when the cistern will be full?
Options:
(A) 17
(B) 16
(C) 28
(D) 13
(E) 12
Reasoning: You have 40 multiples of 5, 8 of 25 and 1 of 125. This will give 49 zeros.
Ans: (C)
Question: How many terminating zeroes E does 200! have?
Options:
(A) 40
(B) 48
(C) 49
(D) 55
(E) 64
Rationale: Average of the first 'n' natural numbers = (n + 1)/2
We get (9 + 1)/2 = 5
The answer: (B)
Question: Find the average of the first 9 natural numbers?
Options:
(A) 8
(B) 5
(C) 10
(D) 11
(E) 12
Reasoning: 1/3: 1/7: 1/1 = 7:3:21
Ans: (E)
Question: The inverse ratio of 3: 7: 1 is?
Options:
(A) 2:3:7
(B) 2:3:9
(C) 2:3:2
(D) 2:3:6
(E) 2:3:1
Rationale: Speed = 60 * 5/18 = 50/3 m/sec
Length of the train = speed * time = 50/3 * 9 = 150 m
The answer: (E)
Question: A train running at the speed of 60 km/hr crosses a pole in 9 sec. What is the length of the train?
Options:
(A) 120 m
(B) 180 m
(C) 324 m
(D) Cannot be determined
(E) None of these
Rationale: Maximum points of intersection between n different circles = n*(n - 1) = 45*44 = 1980
The answer: (C)
Question: There are different 45 circles. What is the number of the greatest possible points with which the circles intersect?
Options:
(A) 1950
(B) 2000
(C) 1980
(D) 1580
(E) 2600