第一道——customize a bike by exchanging the front wheel for a wheel that had one half the diameter of th

题目

第一道——customize a bike by exchanging the front wheel for a wheel that had one half the diameter of the back wheel,then when ride the bike,how many revolutions does the front wheel make for each revolution of the back wheel?
C 2
D 1/2
第二道——When 15 is divided by the positive integer k,the remainder is 3,.For how many different values of K is the true?我觉得是4个（1,2,3,4）,但答案给的是3个,为什么,哪里错了?

答案

第一道
C
直径是一半,所以周长是一半,所以要走相同的距离要有2倍的转速.
第二道
15被一个正整数除余3,所以这个数12的因数.所以可以是4,6,12.总共3个.