question: There are a total of 15 numbers with an average of 11. The average of first seven numbers is 14 and the average of last seven numbers is 6. What is the middle number?
Options:
(A) 31
(B) 24
(C) 29
(D) 25
(E) 21
answer: Stream of consciousness: The total of 15 numbers = 15X11 = 165
The total of first 7 and last 7 numbers is = 7 X 14+7 X 6 = 140
So, the middle number is (165 - 140 ) = 25 The answer is (D).

q: A motorcyclist goes from Bombay to Pune, a distance of 192 kms at an average of 32 kmph speed. Another man starts from Bombay by car 2 hours after the first, and reaches Pune hour earlier. What is the ratio of the speed of the motorcycle and the car?
Options:
(A) 1:2
(B) 1:7
(C) 1:9
(D) 1:5
(E) 1:1
a: Stream of consciousness: T = 192/32 = 6 h
T = 6 - 3 = 3
Time Ratio = 6:3 = 2:1
Speed Ratio = 1:2 The answer is (A).

question: Which of the following is equal to the average (arithmetic mean) of (x+5)^2 and (x-5)^2?
Options:
(A) x^2
(B) x^2+2
(C) x^2 +30
(D) x^2+20
(E) x^2+25
answer: Stream of consciousness: Avg = [(x+5)^2 + (x-5)^2] / 2
Expanding and simplifying, (x^2 + 10x + 25 + x^2 - 10x + 25) / 2 = x^2 + 25 The answer is (E).

q: A pipe can fill a cistern in 20 minutes whereas the cistern when fill can be emptied by a leak in 30 minutes. When both pipes are opened, find when the cistern will be full?
Options:
(A) 17 minutes
(B) 87 minutes
(C) 60 minutes
(D) 27 minutes
(E) 11 minutes
a: Stream of consciousness: 1/20 - 1/30 = 1/60
60 minutes The answer is (C).

question: What will come in place of the x in the following Number series? 2, 7, 27, 107, 427, x
Options:
(A) 1427
(B) 1607
(C) 1707
(D) 2047
(E) 2147
answer: Stream of consciousness: 2
2 4 - 1 = 7
7 4 - 1 = 27
27 4 - 1 = 107
107 4 - 1 = 427
427 4 - 1 = 1707 The answer is (C).

question: A man rows his boat 95 km downstream and 45 km upstream, taking 2 1/2 hours each time. Find the speed of the stream?
Options:
(A) 10 kmph
(B) 6 kmph
(C) 5 kmph
(D) 8 kmph
(E) 7 kmph
answer:
Stream of consciousness: Speed downstream = d/t = 95/(2 1/2) = 38 kmph
Speed upstream = d/t = 45/(2 1/2) = 18 kmph
The speed of the stream = (38 - 18)/2 = 10 kmph The answer is (A).