Question

A bag contains 9 discs of which 4 are red, 3 are blue and 2 are yellow. The discs are similar in shape and size. A disc is drawn at random from the bag. Calculate the probability that it will be either red or blue.

Answer 1

the probability that it will be either red or blue is 7/9

Explanation:

There are 9 disks altogether. Since there are 4 red disks, the probability that a red disk will be drawn is 4/9. The probability that a blue disk will be drawn is 3/9. These two events are independent of one another.

The probability that it will be either red or blue is that of the union of the two events. Thus, we add together 4/9 and 3/9, obtaining 7/9