Q: Fill in the blank with the correct number in this number series: 5, 15, 7, 12, __, 9, 11,... ?
Options:
(A) 6
(B) 9
(C) 8
(D) 7
(E) 5
A: OK... Stream of consciousness: In this simple alternating subtraction and addition series; The first series begins with 5 and adds 2; the second begins with 15 and subtracts 3, and so on.
The answer is (B).

Q: P and Q can complete a work in 20 days and 12 days respectively. P alone started the work and Q joined him after 4 days till the completion of the work. How long did the work last?
Options:
(A) 5 days
(B) 9 days
(C) 30 days
(D) 20 days
(E) 10 days
A: OK... Stream of consciousness: Work done by P in 1 day = 1/20
Work done by Q in 1 day = 1/12
Work done by P in 4 days = 4 (1/20) = 1/5
Remaining work = 1 1/5 = 4/5
Work done by P and Q in 1 day = 1/20 + 1/12 = 8/60 = 2/15
Number of days P and Q take to complete the remaining work = (4/5) / (2/15) = 6
Total days = 4 + 6 = 10
The answer is (E).

Q: The area of a triangle is with base 10m and height 5m?
Options:
(A) 11
(B) 25
(C) 787
(D) 122
(E) 12
A: OK... Stream of consciousness: 1/2 * 10 * 5 = 25 m2
The answer is (B).

Q: In one hour, a boat goes 11 km/hr along the stream and 5 km/hr against the stream. The speed of the boat in still water (in km/hr) is:
Options:
(A) 3
(B) 4
(C) 5
(D) 8
(E) 9
A:
OK... Stream of consciousness: Speed in still water = (11 + 5)/2 kmph = 8 kmph.
The answer is (D).