Rationale: This alternating addition series begins with 3; then 1 is added to give 4; then 3 is added to give 7; then 1 is added, and so on.
The answer: (A)
Question: Look at this series: 3, 4, 7, 8, 11, 12, ... What number should come next?
Options:
(A) 15
(B) 14
(C) 17
(D) 12
(E) 19
Reasoning: 10 * 15 + 36 26 = 160/10 = 16
Ans: (C)
Question: The average of 10 numbers is calculated as 15. It is discovered later on that while calculating the average, one number namely 36 was wrongly read as 26. The correct average is?
Options:
(A) 22
(B) 88
(C) 16
(D) 83
(E) 82
Rationale: S = 600/40 = 15 mps
S = 3600/15 = 240 sec = 4 min
The answer: (A)
Question: A 600 meter long train crosses a signal post in 40 seconds. How long will it take to cross a 3 kilometer long bridge, at the same speed?
Options:
(A) 4 min
(B) 2 min
(C) 8 min
(D) 9 min
(E) 5 min
Reasoning: S = 560/16 * 18/5 = 126 kmph
Ans: (A)
Question: A train 560 m in length crosses a telegraph post in 16 seconds. The speed of the train is?
Options:
(A) 126 kmph
(B) 77 kmph
(C) 54 kmph
(D) 71 kmph
(E) 88 kmph
Rationale: The differences between two successive terms from the beginning are 7, 5, 7, 5, 7, 5. So, 40 is wrong.
The answer: (C)
Question: Find the invalid no.from the following series 13, 18, 25, 30, 37, 40
Options:
(A) 13
(B) 18
(C) 40
(D) 37
(E) 40
Rationale: T = 40/36 * 18/5 = 4 sec
The answer: (D)
Question: In what time will a railway train 40 m long moving at the rate of 36 kmph pass a telegraph post on its way?
Options:
(A) 3
(B) 5
(C) 9
(D) 4
(E) 7