Aptitude Day 143

Problems on Probability:

1. A bag contains 4 red, 1 blue and 2 green balls. Two balls are drawn at random. What’s the probability that none of the balls are blue?

Solution:

                  Total Balls = 4+2+1 = 7

                  n(S) = ⁷C₂ =  21.

                  n(E) = ⁶C₂ = 15

                      

                  P(E) = n(E)/ n(S)

                         = 15/21

                         = 5/7.

2. In a box, there are 6 red, 8 blue and 5 green balls. One ball is picked up randomly. What’s the probability that it is neither or blue?

Solution:

                Total Balls = 6+8+5 = 19

                  n(S) = ¹⁹C₁ =  19

                  n(E) = ⁵C₁  = 5

                      

                  P(E) = n(E)/ n(S)

                         = 5/19.