question: Pipes A and B can fill a cistern in 8 and 24 minutes respectively. They are opened an alternate minutes. Find how many minutes, the cistern shall be full?
Options:
(A) 12 min
(B) 6 min
(C) 4 min
(D) 8 min
(E) 10 min
answer: Stream of consciousness: 1/8 + 1/24 = 1/6
6 * 2 = 12 The answer is (A).
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question: Find the average of the first 25 natural numbers?
Options:
(A) 8
(B) 9
(C) 13
(D) 11
(E) 12
answer: Stream of consciousness: Average of the first 'n' natural numbers = (n + 1)/2
We get (25 + 1)/2 = 13 The answer is (C).
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question: A cricket bat is sold for $900, making a profit of $300. The profit percentage would be
Options:
(A) 24%
(B) 25%
(C) 30%
(D) 50%
(E) 40%
answer: Stream of consciousness: 300/(900 - 300) = 50%. The answer is (D).
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question: Two trains are traveling on parallel tracks in the same direction. The faster train travels at 150 miles per hour, while the slower train travels at 100 miles per hour. At 2 o'clock the faster train is 10 miles behind the slower one. How far apart are the two trains at 5 o'clock?
Options:
(A) 60 miles
(B) 80 miles
(C) 90 miles
(D) 140 miles
(E) 400 miles
answer:
Stream of consciousness: Answer = D. 140 miles
Relational speed = 150 - 100 = 50 miles per hour
In 3 hours, difference = 50 * 3 = 150 miles
Fast train trailing 10 miles, so effective difference = 150 - 10 = 140 miles The answer is (D).
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