Probability study guide

Examples: If you role a die: P(6)

1/6

P(4 or 6)

2/6=1/3

A bag contains 2 red, 3 green and 2 blue balls. Two balls are drawn at random. What is the probability that none of the balls drawn is blue? A. 10/21 B. 11/21 C. 2/7 D. 5/7

A

A bag contains 2 red, 3 green and 2 blue balls. Two balls are drawn at random. What is the probability that none of the balls drawn is blue? A. 10 - 21 B. 11 - 21 C. 2 - 7 D. 5 - 7

A

In a box, there are 8 red, 7 blue and 6 green balls. One ball is picked up randomly. What is the probability that it is neither red nor green? A. 1/3 B. 3/4 C. 7/19 D. 8/21 E. 9/21

A

What is the probability of getting a sum 9 from two throws of a dice? A. 1/6 B. 1/8 C. 1/9 D. 1/12

C

Choosing a day of the week with the letter A in it

CERTAIN

Choosing a week of the day with "Day" at the end

Certain

Three unbiased coins are tossed. What is the probability of getting at most two heads? A. 3/4 B. 1/4 C. 3/8 D. 7/8

D

Tickets numbered 1 to 20 are mixed up and then a ticket is drawn at random. What is the probability that the ticket drawn has a number which is a multiple of 3 or 5? A. 1/2 B. 2/5 C. 8/15 D. 9/20

D

Tickets numbered 1 to 20 are mixed up and then a ticket is drawn at random. What is the probability that the ticket drawn has a number which is a multiple of 3 or 5? A. 1 - 2 B. 2 - 5 C. 8 - 15 D. 9 - 20

D

Not drinking water in four days

Impossible

Rolling a 12 on a regular die

Impossible

You solve a brain teaser .89 of the time

Likely

Determine the probability that a digit chosen at random from the digits 1, 2, 3, ...12 will be odd. 1. 1/2 2. 1/9 3. 5/94. 4/9

Option one

event

The thing you want to occur

There's a 3% chance of snow

Unlikely

The sun will come out once a day

certain

Probability

likelihood that a particular event will occur

Outcome

result