Question

A bag has 20 marbles numbered 1, 2, 3,..., 20. One marble is randomly drawn. Find the probability that the number on the marble is: a. Even c. Multiple of 4 b. Greater than 4 d. Not even

Answer 1

Given that, a bag has 20 marbles numbered 1, 2, 3,...., 20. One marble is randomly drawn.

We want to find the following probabilities,

a) There are 10 even mumbers in 20 marbles, that are, { 2, 4, 6, 8, 10, 12, 14, 16, 18, 20}

Therefore, P(even) = 10/20 = 0.5

The probability that the number on the marble is even is 0.5

b) There are, 5 numbers that are multiple of 4: { 4, 8, 12, 16, 20}

Therefore, P(multiple of 4) = 5/20 = 0.25

The probability that the number on the marble is multiple of 4 is 0.25

c) There are, 16 numbers that are greater than 4

Therefore, P(greater than 4) = 16/20 = 0.8

The probability that the number on the marble is greater than 4 is 0.8

d) There are 10 numbers that are not even (odd) :

{1, 3, 5, 7, 9, 11, 13, 15, 17, 19}

Therefore, P(not even) = 10/20 = 0.5

The probability that the number on the marble is not even is 0.5