Problem Solving
试题详情
题目：
A three-digit code for certain logs uses the digits 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 according to the following constraints. The first digit cannot be 0 or 1, the second digit must be 0 or 1, and the second and third digits cannot both be 0 in the same code. How many different codes are possible?
选项:
A、144
B、152
C、160
D、168
E、176
答案:
B
提问：
这道题目题库没有，想请老师帮忙解答下。答案是300,000
A real estate agent sold five houses during the past month. The median sales price of these houses was $150,000 and the average (arithmetic mean) sales price was $200,000. The sales price of the most expensive house was at least three times the sales price of the least expensive house. Based on the information provided, what is the minimum possible sales price for the most expensive house?
想了很久，如果是求最大的数的最小值，那么其他的数就要取最大，如果把房子设为：x1 x2 x3 x4 x5 x6 x7,则x4=150,000.要使得其他的数最大，那么x1,x2,x3就要取到150000，x5,x6这个时候应该怎么想呢？ 还有那个题目中最大的数与最小的数有个限定条件我不会用。
评分:
0
浏览:
4647
提问：
问一道机经题目，请问这个题目的那个出现第一次和第二次正面的组合为什么是2*2*2*2呀。这种题目答案都看不明白..... 请求老师解答一下，排列组合一直是弱项[img=/resource/2018-09/1029-1536280418.png]
评分:
0
浏览:
4909
