question:If X is the sum of first 30 positive even integers and Y is the sum of first 30 positive odd integers, what is the value of x-y?
Please try to explain your answers
Options:
(A) 10
(B) 25
(C) 30
(D) 75
(E) 100
answer:(C)
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 30 positive even integers minus the sum of first 30 positive odd integers will be 30.

question:What amount does Kiran get if he invests Rs. 18000 at 15% p.a. simple interest for four years?
Options:
(A) 22777
(B) 28877
(C) 26888
(D) 28800
(E) 67881
answer:(D)
Stream of consciousness:Simple interest = (18000 * 4 * 15)/100 = Rs. 10800
Amount = P + I = 18000 + 10800 = Rs. 28800

question:If the personal income tax rate is lowered from 45% to 30%, what is the differential savings for a tax payer having an annual income before tax to the tune of $48000?
Options:
(A) $3500
(B) $5000
(C) $3150
(D) $7200
(E) $10000
answer:
(D)
Stream of consciousness:Saving = (45-30)% of 48000 = 7200.