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) 3
answer: Stream of consciousness: 1 to 9 = 9 * 9 = 81
1 to 5 = 5 * 10 = 50
5 to 9 = 5 * 8 = 40
5th = 50 + 40 = 90 – 81 = 9 The answer is (A).


q: Look at this series: 664, 332, 340, 170, ____, 89, ... What number should fill the blank?
Options:
(A) 85
(B) 97
(C) 109
(D) 178
(E) 112
a: Stream of consciousness: Answer: Option D
This is an alternating division and addition series: First, divide by 2, and then add 8. The answer is (D).


question: Divide Rs.32000 in the ratio 3:5?
Options:
(A) 12000,20000
(B) 12000,20092
(C) 12000,20029
(D) 12000,20007
(E) 12000,20001
answer: Stream of consciousness: 3/8 * 32000 = 12000
5/8 * 32000 = 20000 The answer is (A).


q: The average of first 13 natural numbers is?
Options:
(A) 5.2
(B) 5.5
(C) 7
(D) 9
(E) 10
a: Stream of consciousness: Sum of 13 natural no. = 182/2 = 91
Average = 91/13 = 7 The answer is (C).


question: If a man can cover 20 metres in one second, how many kilometres can he cover in 3 hours 45 minutes?
Options:
(A) 288
(B) 162
(C) 220
(D) 270
(E) 122
answer: Stream of consciousness: 20 m/s = 20 * 18/5 kmph
3 hours 45 minutes = 3 3/4 hours = 15/4 hours
Distance = speed * time = 20 * 18/5 * 15/4 km = 270 km. The answer is (D).


question: A pipe can fill a cistern in 20 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) 76 minutes
(B) 29 minutes
(C) 70 minutes
(D) 17 minutes
(E) 98 minutes
answer:

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.
user
Stream of consciousness: 1/20 - 1/28 = 1/70
70 minutes The answer is (C).