Calculate the Probability
A bag contains 80 balls of such 20 are red, 25 are blue and 35 are white. A ball is picked at random what is the probability that the ball picked is as:
(i) Red ball
(ii) Black ball
(iii) Red or Blue ball.
Solution
(i) Probability of a red ball = number of red ball in the bag/total balls in the bag
= P(R)
= 20/80
= 1/4
(ii) Probability of black ball = number of red ball in the bag/total balls in the bag
= P (B)
= 0/80
= 0
(iii) P(R or B) = 20/80 or 25/80 = 20/80 + 25/80
= 9/16
Note: in probability or is replaced by a plus (+) sign. Look addition rule.