q: The average of seven numbers is 26. 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) 83
(C) 29
(D) 32
(E) 34
a: Stream of consciousness: The total of seven numbers = 7X26 = 182
The total of first 3 and last 3 numbers is = 3 X 14+3 X 19 = 99
So, the middle number is (182 - 99 ) = 83 The answer is (B).

question: 95 white and black tiles will be used to form a 10x10 square pattern. If there must be at least one black tile in every row and at least one white tile in every column, what is the maximum difference between the number of black and white tiles that can be used?
Options:
(A) 75
(B) 80
(C) 85
(D) 90
(E) 95
answer: Stream of consciousness: Answer = C
Please refer diagram below
95 - 10 = 85 The answer is (C).

q: 4000 was divided into two parts such a way that when first part was invested at 3% and the second at 5%, the whole annual interest from both the investments is Rs.144, how much was put at 3%?
Options:
(A) 2800
(B) 2500
(C) 2700
(D) 3000
(E) 3500
a: Stream of consciousness: (x*3*1)/100 + [(4000 - x)*5*1]/100 = 144
3x/100 + 200 5x/100 = 144
2x/100 = 56 e x = 2800 The answer is (A).

question: Find 12 19
Options:
(A) 238
(B) 228
(C) 208
(D) 277
(E) 101
answer: Stream of consciousness: Mentally imagine this number as (10 + 2 ) 19 = 190 + 38 = 228. The answer is (B).

q: The average of 13 result is 20. Average of the first 8 of them is 20 and that of the last 8 is 40. Find the 8th result?
Options:
(A) 35
(B) 37
(C) 46
(D) 90
(E) 100
a: Stream of consciousness: Sum of all the 13 results = 13 * 20 = 260
Sum of the first 7 of them = 8 * 20 = 160
Sum of the last 7 of them = 8 * 40 = 320
So, the 8th number = 260 + 160 - 320 = 100. The answer is (E).

q: Two pipes A and B can fill a cistern in 20 and 30 minutes respectively, and a third pipe C can empty it in 50 minutes. How long will it take to fill the cistern if all the three are opened at the same time?
Options:
(A) 17 1/4 min
(B) 28 1/7 min
(C) 17 1/7 min
(D) 17 1/8 min
(E) 15 15/19 min
a:
Stream of consciousness: 1/20 + 1/30 - 1/50 = 19/300
300/19 = 15 15/19 The answer is (E).