421、If a number between 0 and 1/2 is selected at random，which of the following will the number most likely be between？
A、0 and 3/20 B、3/20 and 1/5 C、1/5 and 1/4 D、1/4 and 3/10 E、3/10 and 1/2
答案是E
解释是这样的
Each of the given pairs of numbers defines a segment of the number line between 0 and 1/2,and the length of each segment is found by subtracting the first number from the second.The number selected is most likely to be in the longest of these segments.Therefor ,it is most likely that the number selected will be between the given paire of numbers whose difference is greatest.To compare the five differences most easily,one can use 20 as a common denominator when computing each difference.The differences would then be 3/20,1/20,1/20,1/20,and 4/20respectively .The best answer is E
我左看右看不明白,哪位大哥能给MM讲讲呀? | 
