Q: Calculate the speed of a boat in still water (in km/hr) if in one hour, the boat goes 15 km/hr downstream and 7 km/hr upstream.
Options:
(A) 12 kmph
(B) 13 kmph
(C) 14 kmph
(D) 15 kmph
(E) 11 kmph
A: OK... Stream of consciousness: Speed in still water = (15 + 7)1/2 kmph = 11 kmph.
The answer is (E).

Q: What is theleast number should be added to 1056, so the sum of the number is completely divisible by 23?
Options:
(A) 1
(B) 2
(C) 3
(D) 4
(E) 5
A: OK... Stream of consciousness: (1056 / 23) gives remainder 21
21 + 2 = 23, So we need to add 2
The answer is (B).

Q: If X is the sum of first 20 positive even integers and Y is the sum of first 20 positive odd integers, what is the value of x-y?
Please try to explain your answers
Options:
(A) 0
(B) 20
(C) 50
(D) 75
(E) 100
A: OK... Stream of consciousness: First even minus first odd = 2-1 = 1;
The sum of first 2 even integers minus the sum of first 2 odd integers = (2+4)-(1+3) = 2;
The sum of first 3 even integers minus the sum of first 3 odd integers = (2+4+6)-(1+3+5) = 3;
We can see the patterns here, so the sum of first 20 positive even integers minus the sum of first 20 positive odd integers will be 20.
The answer is (B).

Q: A farm used two harvesting machines, H and K, to harvest 100 acres of wheat. Harvesting machine H, working alone at its constant rate, harvested 40 acres of wheat in 8 hours. Then harvesting machine K was brought in, and harvesting machines H and K, working together at their respective constant rates, harvested the remaining acres of wheat in 4 hours. Harvesting machine K harvested how many acres of wheat per hour?
Options:
(A) 7
(B) 8
(C) 11
(D) 13
(E) 15
A:
OK... Stream of consciousness: Rate of H = 4 acres/hr
Remaining land to be harvested = 100 - 40 = 60
Rate of H and K = 60/4 = 15 acres/hr
Rate of K = 15- 4 = 11
The answer is (C).