Question

A number is picked randomly in the range [2,8]. If past selection indicates that the numbers picked are less than 5, what is the probability that a number picked will be (a) less than 4 (b) greater than 4. What is the probability that the number picked is 4.5

Answer 1

a) P = 2/7

b) P = 4/7

c) P = 1/7

Explanation:

In the range of [2,8], we have the following integers which are: 2, 3, 4, 5, 6, 7, 8. So this is a total of 7 integers.

a) We look for the probability that the numbers are less than 4, so we conclude that there are possible numbers 2 and 3 out of possible 7, so the required probability is equal to P = 2/7.

b) We look for the probability that the numbers are greater than 4, so we conclude that there are possible numbers 5, 6, 7, 8 out of possible 7, so the required probability is equal to P = 4/7.

c) Based on the previous two examples, we conclude that the required probability is P = 2/7· 1/2=1/7.