121、 补充:定义gap,指一满足条件a<X<b的X的个数,aXb都是整数。求2到29内(inclusive)之间所有质数间的gap的平均值。 a 2.0 b 2.4 c 2.6 d 2.8 e 3.0答案:A 解答:2——26内的质数:2,3,5,7,11,13,17,19,23,29。他们之间的gap分别是:0,1,1,3,1,3,1,3,5。这九个数的平均数是18/9=2 同意
If you need to find the gap between "1" and "3" the gap should be "1" since there can only be "1" "2" and "3" where "2" is missing here. So the gap is "1"
2.)
Gap between 1 and 10 should be "8" -> 2, 3, 4,5,6,7,8,9