提问几道GRE数学题!都是绿皮上的,本人数学不大好,P275.39In how many of the integers between 1 and 100 does the digit 5 occur exactly once?答案是18,题目啥意思,如何做?P231.2A train travels 60 miles per hour for 3 hours and then 45 miles per hour for 2 hours.What is the train's average speed in miles per hour during the 5-hour period?P246.17A teacher has a total of at least 110 students enrolled in her classes.If the teachers has an average of exactly 27 students enrolled per class,what
提问几道GRE数学题!
都是绿皮上的,本人数学不大好,
P275.39
In how many of the integers between 1 and 100 does the digit 5 occur exactly once?
答案是18,题目啥意思,如何做?
P231.2
A train travels 60 miles per hour for 3 hours and then 45 miles per hour for 2 hours.What is the train's average speed in miles per hour during the 5-hour period?
P246.17
A teacher has a total of at least 110 students enrolled in her classes.If the teachers has an average of exactly 27 students enrolled per class,what is the least possible number of classes that the teacher could have?
我算得4呀
在1和100之间的整数有多少，数字5出现一次？
一列火车以每小时60英里的旅行3小时,然后45英里每小时2小时。火车的平均速度是多少在英里每小时在5小时的时间吗?
一个老师一共有至少110名学生参加她的课程。如果老师有平均每个班入学的学生到底27,什么是最少数量的类,老师可以吗?
第一题是问，1到100之间数字5出现的次数，我算的是19次，5，15，25，35，45，55，65……
第二题是求平均速度，60mile3小时，45mile2小时，总共60*3+45*2=270mile，时间5小时，平均速度54
第三题说这个老师收了110个学生在班上，平均每个老师27个学生，问这个老师至少带多少个班，5*27=135大于110是可以的，4*27=108小于110这是不可能的。
GRE的数学题都是很简单的
题目是问在1和100之间的整数中,有多少个5只出现1次.5,15,25,35,45,65,76,85,9550,51,52,53,54,56,67,58,59,共18个(55不算)The total distance is 60*3 + 45*2 = 270 miles,total time is 5 hours,evarage speed is 2...