SOLUTION: Find the probability. A lottery game has balls numbered 1 through 21. What is the probability that a randomly selected ball is an even numbered ball or a 12?

Question 545766: Find the probability.
A lottery game has balls numbered 1 through 21. What is the probability that a randomly selected ball is an even numbered ball or a 12?
Answer by neatmath(302) (Show Source): You can put this solution on YOUR website!

There are 21 balls, numbered 1 through 21.

How many would have even numbers?

2, 4, 6, 8, 10, 12, 14, 16, 18, 20

So there would be 10 with even numbers.

How many would have the number 12?

Just one, the 12.

Now, in probability, the probability of event A OR event B happening,

is the probability of event A plus the probability of event B minus the probability of both A AND B.

Let A be the event of drawing an even number.

Let B be the event of drawing a 12.

In this case then, we are drawing 1 ball only.

P(A)=10/21

P(B)=1/21

P(A and B)=1/21 (because 12 is both 12 AND an even number)

Then P(A or B)=P(A)+P(B)-P(A and B)

P(A or B)=10/21+1/21-1/21

P(A or B)=10/21

There is a LOT more to this subject. Take it slow and read, read, read!

Don't be afraid to ask questions.

I hope this helps! :)

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