再请教几个GWD上的数学题

(1)n is divisible by 3

(2)2n is divisible by twice as many positive integers as n

这一道我只能想出来（1）insufficient，但是（2）怎么举证？我读了半天都没把意思搞清楚……

2. A certain roller coaster has 3 cars, and a passenger is equally likely to ride in any 1 of the 3 cars each time that passenger rides the roller coaster. If a certain passenger is to ride the roller coaster 3 times, what is the probability that the passenger will ride in each of the 3 cars?

这道题我算出来的是1/10，但是答案没有这个选项……唉，再次哀叹自己的概率学的太差了…………