Reasoning: In this addition series, 1 is added to the first number; 2 is added to the second number; 3 is added to the third number; 4 is added to the fourth number; and go on.
Ans: (A)
Question: Look at this series: 201, 202, 204, 207, ... What number should come next?
Options:
(A) 211
(B) 205
(C) 224
(D) 267
(E) 269
Rationale: Average of the first 'n' natural numbers = (n + 1)/2
We get (23 + 1)/2 = 12
The answer: (E)
Question: Find the average of the first 23 natural numbers?
Options:
(A) 8
(B) 9
(C) 10
(D) 11
(E) 12
Reasoning: 1 to 11 = 11 * 44 = 484
1 to 5 = 5 * 49 = 245
5 to 11 = 7 * 52 = 364
5th = 245 + 364 – 484 = 125
Ans: (A)
Question: The average of 11 results is 44, if the average of first five results is 49 and that of the last seven is 52. Find the fifth result?
Options:
(A) 125
(B) 126
(C) 127
(D) 128
(E) 129
Rationale: 8 * 84 = 672 – 7 = 665
The answer: (B)
Question: The average salary of workers in an industry is Rs.200 the average salary of technicians being Rs.400 and that of non-technicians being Rs.125. What is the total number of workers?
Options:
(A) 277
(B) 665
(C) 662
(D) 552
(E) 281
Reasoning: 12 men 120 acres 36 days
54 men ? 54 days
120 * 54/12 * 54/36
10 * 54 * 3/2
54 * 15 = 810
Ans: (C)
Question: If 12 men can reap 120 acres of land in 36 days, how many acres of land can 54 men reap in 54 days?
Options:
(A) 186
(B) 188
(C) 810
(D) 167
(E) 861
Reasoning: In 1 hour it fill 1/20 + 1/12 - 1/20 = 1/12
So fill tank fill up in 12 Hours
Ans: (E)

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.
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Question: Two pipes can fill a tank in 20 and 12 hours, while third pipe will make the tank empty in 20 hours. If all three pipes operate simultaneously. In how many hours the tank will be filled ?
Options:
(A) 5 Hours
(B) 7 Hours
(C) 8 Hours
(D) 9 Hours
(E) 12 Hours