question: Two trains are moving at 80 kmph and 70 kmph in opposite directions. Their lengths are 150 m and 100 m respectively. The time they will take to pass each other completely is?
Options:
(A) 4 sec
(B) 5 sec
(C) 6 sec
(D) 7 sec
(E) 8 sec
answer: Stream of consciousness: 70 + 80 = 150 * 5/18 = 125/3 mps
D = 150 + 100 = 250 m
T = 250 * 3/125 = 6 se The answer is (C).

q: A bullet train 140 m long is running at 60 kmph. In how much time will it pass a platform 410 m long?
Options:
(A) 33 Seconds
(B) 22 Seconds
(C) 41 Seconds
(D) 24 Seconds
(E) 29 Seconds
a: Stream of consciousness: Distance travelled = 140 + 410m = 550m
Speed = 60 * 5/8 = 50/3m
Time = 550 * 3/50 = 33 Seconds The answer is (A).

question: Which of the following expressions are different in value?
(A) (2x + 3y)2
(B) (2x + y)2 + 8y(x + y)
(C) (2x y)2 8y(x + y)
(D) 22(x + y)2 + 4xy + 5y2
Options:
(A) A and B
(B) B and C only
(C) A, B and D only
(D) B and D only
(E) All are different
answer: Stream of consciousness: All others are equal except (C). The answer is (B).

q: The average of 13 numbers is 60. Average of the first 7 of them is 57 and that of the last 7 is 61. Find the 8th number?
Options:
(A) 46
(B) 83
(C) 45
(D) 53
(E) 64
a: Stream of consciousness: Sum of all the 13 numbers = 13 * 60 = 780
Sum of the first 7 of them = 7 * 57 = 399
Sum of the last 7 of them = 7 * 61 = 427
So, the 8th number = 427 + 399 - 780 = 46. The answer is (A).

question: Calculate the speed of a boat in still water (in km/hr) if in one hour, the boat goes 10 km/hr downstream and 4 km/hr upstream.
Options:
(A) 7 kmph
(B) 8 kmph
(C) 9 kmph
(D) 7 kmph
(E) 6 kmph
answer: Stream of consciousness: Speed in still water = (10 + 4)1/2 kmph = 7 kmph. The answer is (A).

question: A password of a computer consists of five digits 1 through 6. What is the probability that all digits are divisible by 3 ?
Options:
(A) 1/3
(B) 1/6
(C) 1/27
(D) 1/243
(E) 1/486
answer:
Stream of consciousness: For each digit there are six possibilities. Two of them (3 and 6) are divisible by three, so there is a one in three chance for each digit, and since the digits are independent of each other, overall probability is 1 / 3^5 or The answer is (D).