A box contains seven red balls and five black balls. Three ballsare selected at random from the box. Compute the probability that(d) at least one ball is red.
Solution
From the question:
A box contains seven red balls and five black balls.
Three balls are selected at random from the box.
Formula:
Probability that at least 1 ball drawn is red = 1 -Probability that none of the 3 balls drawn are red
Probability that none of the 3 balls drawn are red= (5c3) / (12c3)
Apply the formula: nCr = n! / ((n−r)! *r!)
5c3 = 5! / ((5−3)! * 3!) =10
12c3 = 12! / ((12−3)! *
OR
OR