Andy C. answered • 08/11/18
Math/Physics Tutor
After the first spin, there are 3 available colors.
The probability of getting an available color on the second spin is 3/4.
After the second spin, there are 2 available colors.
The probability of getting an available color on the third spin is 2/4.
After the third spin, there is only one available color.
The probability of getting an available color on the fourth spin is 1/4.
If that does not happen, then a 5th spin is required, the proabability
of which is again 1/4.
3/4 * 2/4 * 1/4 * 1/4 = 6/256 = 3/128
