Reasoning: 1 to 9 = 9 * 9 = 81
1 to 5 = 5 * 10 = 50
5 to 9 = 5 * 8 = 40
5th = 50 + 40 = 90 81 = 9
Ans: (A)
Question: The average of 9 observations was 9, that of the 1st of 5 being 10 and that of the last 5 being 8. What was the 5th observation?
Options:
(A) 9
(B) 8
(C) 7
(D) 6
(E) 2
Rationale: In this series, each number is repeated, then 10 is subtracted to arrive at the next number.
The answer: (A)
Question: Look at this series: 53, 53, 43, 43, 33, 33, ... What number should come next?
Options:
(A) A) 23
(B) B) 14
(C) C) 27
(D) D) 53
(E) E) 86
Reasoning: Speed = 45 * 5/18 = 25/2 m/sec
Total distance covered = 410 + 140 = 550 m
Required time = 550 * 2/25 = 44 se
Ans: (C)
Question: A train 410 m long is running at a speed of 45 km/hr. In what time will it pass a bridge 140 m long?
Options:
(A) 40 sec
(B) 50 sec
(C) 44 sec
(D) 49 sec
(E) 60 sec
Rationale: Start with the prime factorization:
33150 = 50*663 = (2*5*5)*3*221 = (2)*(3)*(5^2)*(13)*(17)
There are five distinct prime factors, {2, 3, 5, 13, and 17}
The answer: (B)
Question: How many distinct prime numbers are factors of 33150?
Options:
(A) Four
(B) Five
(C) Six
(D) Seven
(E) Eight
Reasoning: Speed = 60 * 5/18 = 50/3 m/sec
Length of the train = speed * time = 50/3 * 9 = 150 m
Ans: (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) 190 m
(C) 115 m
(D) 110 m
(E) 150 m
Reasoning: Part filled by A + B + C in 1 hour = 1/5 + 1/10 + 1/30 = 1/3
All the three pipes together will fill the tank in 3 hours.
Ans: (C)
Question: Pipe A can fill a tank in 5 hours, pipe B in 10 hours and pipe C in 30 hours. If all the pipes are open, in how many hours will the tank be filled?
Options:
(A) 2
(B) 2.2
(C) 3
(D) 3.5
(E) 4