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16、There are 1200 respondents to a poll, each favoring their preference for candidates A, B, and C. 54% favored A, 48% favored B, and 42% favored C, and there is 30% favored both A and B. Whats the largest possible number of respondents favoring C, but not CB, nor C A. 【答案】12000.28=336 【思路】题目问只选C的最大可能数是多少，要使这个数最大，就要满足所有选C的人，都不会同时选A或者B。即P=1-P=1-=1-=0.28。 17、A plane flied a distance of 800 miles at 360m/h with wind speed. And flied back at 260m/h with wind against it. Whats the average speed of the round-trip? 【答案】约等于302m/h 【思路】将题目理解为单程800m，round-trip 1600m，两个时速中已计入风速的影响，不另行计算。则第一段距离800m，时速360m/h，用时20/9h;第二段距离800m，时速260m/h，用时40/13h。则全程的平均时速=1600/=9360/31,约等于302m/h。 18、To travel trip of 40 miles the speed for the first Y miles was X, and the speed for the remaining 40-y is 1.2X. What average speed? x = 12m/h y = 20m/h 【答案】选c 【思路】根据题意，应该为y = 20m。只有将和的条件合在一起，同时知道两段路程的长度分配和每段路程的速度，此题才有确定的解。 | 
