从小数学就不好的人 12月12号就要考试了 最后的挣扎 prep数学求助

aihuge1000

本人从小数学就不好 我不会的题 在大家看来可能很简单 所以麻烦大家帮我解答一下 马上就考试了 GMAT的数学题 稍微超过小学水平一点的 我基本都不会 很害怕 谢谢啦

１．If C and D are integers,is C even?
       (1)C(D+1)is even
       (2)(C+2)(D+4)is even
答案选C 不明白


2. What is the average height of n people in a group?

(1)The average height of the n/3 tallest people in the group is 6feet 2.5inches,and the average height of the rest of the people in the group is 5 feet10inches.

(2)The sum of the  heights of the n people is 178 feet 9 inches

答案选A 我觉得选D 啊 （2）怎么不对了呢


3.What 's the greatest possible area of a triangular region with one vertex at the center fo a circle of radius 1and the other 2 vertices on the circle.
   A 根号3/4    B1/2     C π/4    D1    E 根号2
答案选B 完全没思路


4.  Five pieces of wood have an average length of 124 centimeters  and a median length of 140 centimeters.What is the maximum possible length of the shortest piece of wood?
 A 90     B 100        C 130         D  140     E 110
 答案选B  数学盲再次发懵了

sdcar2010

１．If C and D are integers,is C even?
      (1)C(D+1)is even
      (2)(C+2)(D+4)is even
(1) If D is odd, then (D +1) is even, then C(D+1) is even in the case when C is odd.
(2) If D is even, then (D + 1) is even, then (C+2)(D+4) is even in the case when C is odd.

Neither 1 or 2 are sufficient.

肉圓兒

12号就考试了~别纠结prep了，直接做狗

sdcar2010

2. What is the average height of n people in a group?

(1)The average height of the n/3 tallest people in the group is 6feet 2.5inches,and the average height of the rest of the people in the group is 5 feet10inches.

(2)The sum of the average height of the n people is 178 feet 9 inches

For (2), it should read as "The sum of the height of the n people is 178 feet 9 inches."

sdcar2010

What 's the greatest possible area of a triangular region with one vertex at the center fo a circle of radius 1and the other 2 vertices on the circle.
  A 根号3/4    B1/2     C π/4    D1    E 根号2

You have to draw a triangle within a circle, one vertex is at the center while the other two on the circle.  Then the base of the trangle is one of the radius of the circle with a value of 1. Now you want to find the biggest value for the height of the triangle, which could not be bigger than the radius of the same circle.  So the height is 1.  Then the area = (1 x 1)/2 =1/2

sdcar2010

4.  Five pieces of wood have an average length of 124 centimeters  and a median length of 140 centimeters.What is the maximum possible length of the shortest piece of wood?
A 90     B 100        C 130         D  140     E 110

In this question, you have a median of 140, which is the #3 longest branch.  Two branches will be shorter than 140, while two other branches will be longer than 140. If you know the average of 5 branches is 124, you know the total length is 620.  To get the biggest value for the shortest branch, you need to have the two longest branches as short as possible.  So they both have to be 140.  Therefore the total length of the two shortest branches are 620 - 140 - 140 -140 = 200.  Then the biggest number for the shortest branch is simply 200/2 = 100.

sdcar2010

In most math problems, it is more a logic puzzle than a mere calculation.  Use common sense to help puzzles whenever you can.

aihuge1000

不好意思 我打错了 应该是2)The sum of the  heights of the n people is 178 feet 9 inches

aihuge1000

非常感谢 麻烦你了

sdcar2010

不好意思 我打错了 应该是2)The sum of the  heights of the n people is 178 feet 9 inches

-- by 会员 aihuge1000 (2010/12/6 10:26:49)

In that case, the average height = 178'9" / n; since n is unknown, the average is unknown.  So 2 is not sufficient.