GMAT 오답노트 : Quantitative

CAT2

If a + b = c, what is the value of a?

(1) c – 4 = b + 10 (equation 문제에서는 구조를 바꿔본다 c-b=14) 
(2) b = 6

		Statement (1) BY ITSELF is sufficient to answer the question, but statement (2) by itself is not.
		Statement (2) BY ITSELF is sufficient to answer the question, but statement (1) by itself is not.
		Statements (1) and (2) TAKEN TOGETHER are sufficient to answer the question, even though NEITHER statement BY ITSELF is sufficient.
		EITHER statement BY ITSELF is sufficient to answer the question.
		Statements (1) and (2) TAKEN TOGETHER are NOT sufficient to answer the question, requiring more data pertaining to the problem.

If x, y, and z are 3 different prime numbers, which of the following CANNOT be a multiple of any of x, y, and z? ( can be 이면 답안에서 삭제: picking number 사용시엔 모든 보기 시도.)

		x + y
		y – z
		xy + 1
		xyz + 1
		x2 + y2

Each of 4 bags contains 25 blue disks, 25 green disks, 25 orange disks, 25 yellow disks, and nothing else. If one disk is chosen at random from each of the four bags, what is the probability that the number of blue disks chosen will be no less than 1 and no greater than 3? (최소 1개 to 최대 3개 => nothing and all 로 바꿔서)

A card game called “high-low” divides a deck of 52 playing cards into 2 types, “high” cards and “low” cards. There are an equal number of “high” cards and “low” cards in the deck and “high” cards are worth 2 points, while “low” cards are worth 1 point. How many ways can you draw “high” and “low” cards to earn 5 points if you must draw exactly 3 “low” cards? (combination 문제)

		1
		2
		3
		4
		5

What is the volume, in cubic feet, of one floor of a rectangular office building if this floor has length x feet, width y feet, and height z feet?

(1) 
(2) The area of the ceiling on this floor is 120 square feet and the area of each of two facing walls on this floor is 100 square feet. (xy=100 or yz=100)

		Statement (1) BY ITSELF is sufficient to answer the question, but statement (2) by itself is not.
		Statement (2) BY ITSELF is sufficient to answer the question, but statement (1) by itself is not.
		Statements (1) and (2) TAKEN TOGETHER are sufficient to answer the question, even though NEITHER statement BY ITSELF is sufficient.
		EITHER statement BY ITSELF is sufficient to answer the question.
		Statements (1) and (2) TAKEN TOGETHER are NOT sufficient to answer the question, requiring more data pertaining to the problem.

Nine positive integers are contained in Set N. The median of Set N is the integer x, and all the values in Set N are 3x or smaller. What is the largest possible average (arithmetic mean) of set N?
(If we know that the median is x, that means there must be 4 numbers less than or equal to x and 4 numbers greater than or equal to x)
또해석을 잘 못해서 틀린문제: 미디언(가운데 있는 수)가 X 나머지도 X가 될 수 있다.

		x
		3x

A crate measures 4 feet by 8 feet by 12 feet on the inside. A stone pillar in the shape of a right circular cylinder must fit into the crate for shipping so that it rests upright when the crate sits on at least one of its six sides. What is the radius, in feet, of the pillar with the largest volume that could still fit in the crate?
계산실수

		2
		4
		6
		8
		12

If the vertices(vertex:꼭지점 의복수) of quadrilateral PQRS above lie on the circumference of a circle, is PQRS a square? (yes/no question)

(1) Side PS is equal in length to a radius of the circle. =No! (S)
(2) The degree measure of minor arc QR is 60. =No!(S)

		Statement (1) BY ITSELF is sufficient to answer the question, but statement (2) by itself is not.
		Statement (2) BY ITSELF is sufficient to answer the question, but statement (1) by itself is not.
		Statements (1) and (2) TAKEN TOGETHER are sufficient to answer the question, even though NEITHER statement BY ITSELF is sufficient.
		EITHER statement BY ITSELF is sufficient to answer the question.
		Statements (1) and (2) TAKEN TOGETHER are NOT sufficient to answer the question, requiring more data pertaining to the problem.

Arcs are grouped into two descriptive categories:  1) minor arc  2) major arc  In the circle on the left, there is both a major arc and a minor arc. Look at the circle and try to figure out how you would divide it into a portion that is 'major' and a portion that is 'minor'.    Identify arcs
Identify the major and minor arcs in the circle below.    Answer    The measure of an arc = the measure of its central angle. Therefore the measure of =85 The measure of =360° −85°=275°  Bill spends two days driving from Point A to Point B . On the first day, he drove 2 hours longer and at an average speed 5 miles per hour faster than he drove on the second day. If during the two days he drove a total of 680 miles over the course of 18 hours, what was his average speed on the second day, in miles per hour? 20 25 28 30 35 이틀이라고 48시간이 아닌 총 18시간 운전함. 차분하게 풀었으면 되는 문제. 표를 그려서 문제를 풀면 좋을 것같음. If , which of the following is not a possible value for y? 2 3 If x > y, is zx > yx? (1) z > 0 (2) y < 0 Statement (1) BY ITSELF is sufficient to answer the question, but statement (2) by itself is not. Statement (2) BY ITSELF is sufficient to answer the question, but statement (1) by itself is not. Statements (1) and (2) TAKEN TOGETHER are sufficient to answer the question, even though NEITHER statement BY ITSELF is sufficient. EITHER statement BY ITSELF is sufficient to answer the question. Statements (1) and (2) TAKEN TOGETHER are NOT sufficient to answer the question, requiring more data pertaining to the problem.