Bob plays a game where, for some number n , he chooses a random integer between 0 and n-1 , inclusive. If Bob plays this game for each of the first four prime numbers, what is the probability that the sum of the numbers he gets is greater than 0?

Guest Aug 26, 2018

#2**+1 **

The first four prime numbers are 2,3,5,7

So for the first game, he chooses either 0 or 1

For the second one, he chooses 0,1, or 2

For the third, he chooses 0,1,2,3 or 4

For the fourth, he chooses 0,1,2,3,4,5, or 6

There are a total of \(2*3*5*7=210\)choices

There is only one case where the sum is zero

So there are 209 cases where the sum is greater than zero

The probability that the sum is greater than zero is thus \(209/210\)

Guest Aug 26, 2018