question:A car traveled from San Diego to San Francisco at an average speed of 48 miles per hour. If the journey back took twice as long, what was the average speed of the trip?
Options:
(A) 24.
(B) 32.
(C) 36
(D) 42.
(E) 44.
answer:(B)
Stream of consciousness:Let the time taken be = x
One way distance = 48x
Total distance traveled = 2 * 48x = 96x
Total time taken = x + 2x = 3x
Average speed = 96x/3x = 32

question:The average of seven numbers is 18. The average of first three numbers is 14 and the average of last three numbers is 19. What is the middle number?
Options:
(A) 25
(B) 27
(C) 29
(D) 32
(E) 34
answer:(B)
Stream of consciousness:The total of seven numbers = 7X18 = 126
The total of first 3 and last 3 numbers is = 3 X 14+3 X 19 = 99
So, the middle number is (126 - 99 ) = 27

question:Two trains are moving at 45kmph 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) 40/6 sec
(B) 43/6 sec
(C) 47/6 sec
(D) 40/3 sec
(E) 40/7 sec
answer:
(C)
Stream of consciousness:70 + 45 = 115 * 5/18 = 575/18 mps
D = 150 + 100 = 250 m
T = 250 * 18/575 = 15/2 = 47/6 se