明天考试,确认一下MATH JJ的答案,大家帮忙~~谢谢

lougangs

116. 一个什么读书俱乐部的人，每人每年读5本fiction story books和6本nonfiction story books，年末各选两本来给个杂志写感想，有多少种选法

答案是: 150?  

选课，选物理的肯定选数学，选物理的肯定不选经济，经济与数学都选的有17人，如果选物理的人有15人，选经济的有22人，那么选数学的就有35人，问有多少至少选择一门课程

答案是: 40?

1.      K集合含有６个数，最大的数减去median是４，问median是否一定大于average

(1)median +最大的数＝３４

(2)median和最小的数相差１０

1.      M bought several pencils. if each pencil was either a 23-cent pencil or a 21-cent pencil, how many 23-cent pencils did M buy?

1)M bought a total of 6 pencils

2)the total value of the pencils M bought was 130 cents

B?

1.      if 500 is the multiple of 100 that is closest to x and 400 is the multiple of 100 that is closest to y, which multiple of 100 is closest to x+y?

1)x<500

2)y<400

不懂他说的啥...

[此贴子已经被作者于2008-10-24 9:54:36编辑过]

shengt1984

(5 c 2) * (6 c 2) = 10 * 15 = 150
____________________________________
{a b c d e f } 
median: (c+d)/2
maximum = f
f-(d+c)/2 = 4
(1) (d+c)/2 + f = 34
 --->  f = 19      median = 15 &  (c+d) = 30
(2) minimum = median - 10
     a = 5
a = 5 b =? c+d = 30 e =? f = 19
74 (b=5, e = 15) <a+b+c+d+e+f < 88 (b=15, e = 19)
15 > 74/6  & 15 > 88 / 6

C
_______________________________________________
130 = 23a + 21b
a=2, b =4  is the only solution

_______________________________________________

450 < x < 550
350 < y < 450
800 < x+ y < 1000

1) x < 500    say x = 475   475 + 350 =~ 800 & 475 + 450 ~ 900    (1) alone can not
2) for the same reason                                                                        (2) alone can not

(1) & (2)  450 + 350 =~ 800
                490 + 390 =~ 900
        (1) & (2) together can not

E

shengt1984

physics & econ & math = 0
physics & math = 15
math & econ = 17
physics & econ = 0

math = 35-17-15 = 3
econ = 22 - 17 = 5

all together 15+17+3+5 = 40

lougangs

谢谢LS的讲解,很清楚.