At 15:00 there were 20 students in the computer lab. At 15:03 and every three minutes after that, 3 students entered the lab. If at 15:10 and every ten minutes after that 7 students left the lab, how many students were in the computer lab at 15:44 ?
Options:
(A) 7
(B) 14
(C) 25
(D) 27
(E) 30

Initial no of students + 3 * (1 + No of possible 3 minute intervals between 15:03 and 15:44) -
8 *(1 + No of possible 10 minute intervals between 15:10 and 15:44)
20 + 3*14 -8 * 4 = 25 So the answer is: (C).

What number comes next in the following number series? 12, 50, 202, 810, 3242, _____
Options:
(A) 12400
(B) 12800
(C) 12970
(D) 13015
(E) 16000

12
12 4 + 2 = 50
50 4 + 2 = 202
202 4 + 2 = 810
810 4 + 2 = 3242
3242 4 + 2 = 12970 So the answer is: (C).

The compound ratio of 2/3, 6/7, 4/3 and 1/8 is given by?
Options:
(A) 2/21
(B) 1/48
(C) 1/98
(D) 1/96
(E) 1/68

2/3 * 6/7 * 4/3 * 1/8 = 48/504 = 2/21 So the answer is: (A).

The volume of a certain substance is always directly proportional to its weight. If 48 cubic inches of the substance weigh 112 ounces, what is the volume, in cubic inches, of 53 ounces of this substance?
Options:
(A) 27
(B) 36
(C) 42
(D) 22
(E) 147
112 ounces of a substance has a volume of 48 cubic inches
53 ounces of a substance has a volume of (48/112)*53 = 22 cubic inches So the answer is: (D).