Question 366312
100/100 * 99/100 * 98*100 * ... * 81/100 = Probability that no-one is assigned the same question.
=100!/(80!*100^20)
=.13
1-.13=.87 the probability that at least 2 of the 20 are assigned the same first question.
.
This question is similar to the birthday problem which states that if 23 people are in a room it is statistically likely that 2 have the same birthday.
.
Ed