Question 823005
We are given that the probabilities are independent, and 
let p1 = 1/20, p2 = 1/50, p3 = 1/100, therefore
the probability (P) that all three events occur is small so we multiply the probabilities
P = p1 * p2 * p3
P = (1/20) * (1/50) * (1/100) = (1/100000)
so P is 1 in 100,000