Question

A jar contains 21 balls, labeled 1-21. A ball is randomly selected to determine a lottery winner. What is the probability that the selected ball has an even number or a number less than 10? Justify your answer using the Addition Rule. Write your answer as either a reduced fraction or a decimal rounded to three decimal places.

Answer 1

Answer:

Given,

Jar has 21 balls

Number of possibilities = n = 21

Let us assume A be the event of even number

i.e.,

A = {2,4,6,8,10,12,14,16,18,20} = 10

P(A) = 10/21

B be the event of number less than 10

B = {1,2,3,4,5,6,7,8,9} = 9

P(B) = 9/21

A B = {2,4,6,8} = 4

P(A B) = 4/21

Now addition rule

P(A B) = P(A) + P(B) - P(A B)

substitute values

= 10/21 + 9/21 - 4/21

= 1/21* (10+9-4)

= 1/21*15

= 15/21

P(A B) = 0.714