Probability & Odds

If the odds in favor of an Event are a:b, the probability of that Event is...

• a/(a+b)
• a/(a-b)
• b/(a+b)
• b/(a-b)

If the probability of an Event E is a/b, the odds in favor of that Event are...

• a:(a+b)
• a:(b-a)
• b:(a+b)
• b:(a-b)

In a deck of 52 playing cards what are the odds in favor of drawing a 2, 3, 4, or 5 of diamonds at random?

• 1:12
• 12:1
• 1:13
• 13:1

If all the letters in the alphabet were placed in a bowl, what are the odds against pulling out an “A”, “H”, “R” or “X”? 

• 2:11
• 11:2
• 2:13
• 13:2

What are the odds in favor of randomly selecting a dime from a dish containing 11 pennies, 6 nickels, 5 dimes, and 3 quarters? 

• 4:1
• 1:4
• 1:5
• 5:1

The probability that a team wins the district championship is 20%. What are the odds in favor of the team winning?

• 1:4
• 4:1
• 1:5
• 5:1

There are 7 students in a class: 5 boys and 2 girls.
If the teacher picks a group of 4 at random, what is the probability that everyone in the group is a boy?

• 5/7
• 1/7
• 2/7
• 1

There are 10 students in a class: 5 boys and 5 girls.

If the teacher picks a group of 3 at random, what is the probability that everyone in the group is a girl?

• 1/12

• 1/2

• 1

• 1/5

What is the probability of choosing 2 female senators if there are 19 female senators out of 100?

• 342
• 1/342
• 171
• 1/171

Justin is eating cheeseballs directly out of a vat. There are 45 cheeseballs left, and 4 of them are just balls of cheese dust. What is the probability that Justin grabs at least 1 cheese dust ball when he grabs 5 items from the vat?

• 0.613

• 0.387

• 1,221,759