郁闷之极——GWD15、32、37不懂，请教牛牛们

sasha_wen

Q15:

The average (arithmetic mean) of the 5 positive integers k, m, r
, s, and t is 16, and k < m < r < s < t.  If t is 40, what is the greatest possible value of the median of the 5 integers?


A.    16

B.     18

C.     19

D.    20

E.     22

Answer: B

不知道怎么做？

Q32:

What is the remainder when the positive integer x is divided by 8?

(1)     When x is divided by 12, the remainder is 5.

(2)     When x is divided by 18, the remainder is 11.

                 

A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.

B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.

C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.

D. EACH statement ALONE is sufficient.

E. Statements (1) and (2) TOGETHER are NOT sufficient.

Answer: E

我用的是代入法，但不知有什么高明方法？

Q37:


Of the mutual funds on a “select list,” 1/3 have 5-star ratings, and 2/5 of the remaining funds have 4-star ratings.  If the remaining 300 funds on the list have 3-star ratings, how many funds are on the list?


A.     500

B.     750

C.     1,000

D.     1,200

E.      1,500
Answer: B

数字是凑出来了300/(2/3*3/5)，但是不知道从哪里看出list里只有5星、4星3星

neltharian

1.平均16，那一共是80.所以前4个数之和是80－40＝40.要求第三个数的最大值，那k,m必取最小值1和2，所以r+s=37,又因为s>r,所以r最大取18.
2.两个单独肯定不行，合起来，12k+5=18m+11,化简后是2k-3m=1,发现m只要取正奇数就有解，现在问(18m+11)/8，余数不能确定。（也不是特别好的方法。。。）
3.没看懂楼主问的什么意思。这题就是就一元一次方程(1-1/3)(1-2/5)x=300。

sasha_wen

不知道从哪里看出就只有五星四星三星，要是还有其它的不就不能(1-1/3)(1-2/5)x=300？

machang

the remaining 300 funds on the list have 3-star ratings 貌似就是说除去五星和四星的，剩下的三百家都是三星的........