q: 30 pens and 75 pencils were purchased for 510. If the average price of a pencil was 2.00, find the average price of a pen.
Options:
(A) 10
(B) 11
(C) 12
(D) 13
(E) 14
a: OK... Since average price of a pencil = 2
Price of 75 pencils = 150
Price of 30 pens = (510 150) = 360
Average price of a pen = 36060 = 12
The answer is (C).

q: Four of the five parts numbered as (a), (b), (c), (d) and (e)in the following equations are exactly equal. You have to find out the part that is not equal to the other parts. The number of that part is the answer.
Options:
(A) a2 + 5ab + 6b2
(B) (a + 3b) (a + 2b)
(C) a(a + 3b) + 2b(a + 3b)
(D) (3a + b) (a + 2b)
(E) a(a + 2b) + 3b(a + 2b)
a: OK... The other parts are equal to a2 + 5ab + 6b2.
The answer is (D).

q: 85 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
a:
OK... Answer = A
Please refer diagram below
85 - 10 = 75
The answer is (A).