(Ans). (D)
(Question). If f(x) = x^4/(x^5 - 1), what is f(1/x) in terms of f(x)?
Options:
(A) f(x)
(B) 2*f(x)
(C) 1/f(x)
(D) -f(x)
(E) 2/f(x)
(CoT). If x = 2 then f(x) = 16/31 and f(1/x) = -16/31 which is equal to -f(x)

(Ans). (A)
(Question). If 85 percent of the test takers taking an old paper and pencil GMAT exam answered the first question on a given math section correctly, and 70 percent of the test takers answered the second question correctly, and 5 percent of the test takers answered neither question correctly, what percent answered both correctly?
Options:
(A) 60 %
(B) 65 %
(C) 70%
(D) 75%
(E) 80%
(CoT). {Total} = {First correctly} + {Second correctly} - {Both correctly} + {Neither correctly}
100 = 85 + 70 - {Both correctly} + 5
{Both correctly} = 60.

(Ans). (A)
(Question). The average of 13 numbers is 60. Average of the first 7 of them is 54 and that of the last 7 is 61. Find the 8th number?
Options:
(A) 25
(B) 83
(C) 45
(D) 53
(E) 64
(CoT). Sum of all the 13 numbers = 13 * 60 = 780
Sum of the first 7 of them = 7 * 54 = 378
Sum of the last 7 of them = 7 * 61 = 427
So, the 8th number = 427 + 378 - 780 = 25.

(Ans). (E)
(Question).
? 370 860 1550 2440 3530
Options:
(A) 900
(B) 840
(C) 750
(D) 860
(E) 80
(CoT). 10^2 - 20 = 80
20^2 - 30 = 370
30^2 - 40 = 860
40^2 - 50 = 1550
50^2 - 60 = 2440
60^2 - 70 = 3530.