Question: Two pipes can fill a tank in 20 and 24 minutes respectively and a waste pipe can empty 1 gallons per minute. All the three pipes working together can fill the tank in 15 minutes. The capacity of the tank is?
Options:
(A) 40 gallons
(B) 100 gallons
(C) 120 gallons
(D) 180 gallons
(E) 130 gallons
Answer: Work done by the waste pipe in 1 minute = 1/15 - (1/20 + 1/24) = - 1/40
Volume of 1/40 part = 1 gallonsVolume of whole = 1 * 40 = 40 gallons.
The answer is (A).

Question: A certain number when divided by 45 leaves a remainder 31, what is the remainder if the same number be divided by 15?
Options:
(A) 13
(B) 11
(C) 9
(D) 1
(E) 3
Answer: 45 + 31 = 76/15 = 1 (Remainder)
The answer is (D).

Question: Grace has 18 jellybeans in her pocket. She has 9 red ones, 5 green ones, and 4 blue ones. What is the minimum number of jellybeans she must take out of her pocket to ensure that she has one of each color?
Options:
(A) 4
(B) 8
(C) 12
(D) 13
(E) 15
Answer: The worst scenario is when she takes 9 red and 5 green, total of 14 jellybeans, and still doesn't have 3 distinct colors. But the next draw (15th) will surely be the third color jellybean (blue) as there is no other color jellybeans left in pocket.
The answer is (E).

Question: A telephone company needs to create a set of 3-digit area codes. The company is entitled to use only digits 6, 4 and 3, which can be repeated. If the product of the digits in the area code must be even, how many different codes can be created?
Options:
(A) 20
(B) 22
(C) 26
(D) 24
(E) 30
Answer:
Total # of codes possible is 3*3*3 = 27. Oit of those 27 codes only the product of 333 and will be odd, the remaining 26 will have either 2 or 4 in them, which ensures that their product will be even. Therefore the number of codes where the product of the digits is even = (total) - (restriction) = 27 - 1 = 26.
The answer is (C).