Question

A sample of 100 wood and 100 graphite tennis rackets are taken from the warehouse. if 13 wood and 10 graphite are defective and one racket is randomly selected from the​ sample, find the probability that the racket is wood or defective.

Answer 1

Let's split the problem in non-intersecting subsets: we have
`87` good wood racquets,
`13` defective wood rackets,
`90` good graphite racquets,
`10` defective graphite rackets.

The probability that the racket is wood or defective covers the following subsets: good wood, defective wood and defective graphite, which have, respectively,
`87`,
`13` and
`10` elements.

Since the total is
`200` elements, the probability is

`(87+13+10)/(200) = (110)/(200) = 0.55`