(1)if 500 isthe 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?(选E)

1)x <500

2)y<400

请问这道题的思路是怎样

(2) 没有读懂的一句话

2n is divisible by twice as many positive integer as n

(3)Tanya prepared 4 different letters to be sent to 4 different addresses. for each letter , she prepared an envelope with its correct address. if the 4 letters are to be put into the 4 envelopes at random, what is the probability that only 1 letter will be put into the envelope with its correct address?(I/3)

(4)

Ann   450000

Bob  360000

Cal  190000

Dot  210000

Ed   680000

the table shows the total sales recorded in July for the 5 salespeople at Acme truck sale, it was discovered that one of Cal's sale was incorrectlt recorded as one of Ann's sales. after this error was corrected, Ann's total sales were still higher than Cal's total sale, and the median of the 5 sales total was 330000, what was the value of the incorrectly recorded sale?(120000)

偶是这样想的, 没有变以前, 他们5 个的sale 从小到大排列是: Cal, Dot, Bob, Ann, and Ed, 所以Bob的sale 是media, 为360000,

变化后中位数变成了330000, 其他人的收入都没有变, 所以 Cal 的sale 就变成了330000了啊, 是不是这样啊?

我来给你解一下：

1)closest to the multiple of 100,无非就是这个意思：100N-50<x<100N+50

告诉你X靠近500,那么450<X<500，然后Y靠近400，那么就是。。。。。好了，你自己算吧

2)2n的因数的个数是n的2倍

3)

不是这样啊～ Cal的sale变成330000,不一定哦，有可能是Ann哦，又不一定非要Ann变成中数，而且你的假设也是错误的，谁说其他人收入没有变化啊？cal的错了，弄在Ann头上了，那么Ann的自然也错了。其实中数是Ann，那么变化就是450000-330000=120000，验证一下120000+190000=31000<330000。而你如果cal的sale是330000可就比ann大了，这样验算就知道错了。

谢谢啊，终于弄明白了，那道排列组合的题该怎么做啊？再次讨教.

这题是不是(P22*P22*P22)/P44,正好等于1/3.

有一个信要投对,那只剩下有三封信.然后每一个都只有两个不对的信封可以装,就是P22*P22*P22.分子就是四个信全排.