提问几道GRE数学题!
都是绿皮上的,本人数学不大好,
P275.39
Inhowmanyoftheintegersbetween1and100doesthedigit5occurexactlyonce?
答案是18,题目啥意思,如何做?
P231.2
Atraintravels60milesperhourfor3hoursandthen45milesperhourfor2hours.Whatisthetrain'saveragespeedinmilesperhourduringthe5-hourperiod?
P246.17
Ateacherhasatotalofatleast110studentsenrolledinherclasses.Iftheteachershasanaverageofexactly27studentsenrolledperclass,whatistheleastpossiblenumberofclassesthattheteachercouldhave?
我算得4呀