Bunuel wrote:

What is the probability of rolling three fair dice and having at least one of the three dice show an even number?

A. 35/36

B. 7/8

C. 1/8

D. 1/36

E. 1/216

We want P(select at least 1 even number)

When it comes to probability questions involving "

at least," it's usually best to try using the

complement.

That is, P(Event A happening) = 1 - P(Event A

not happening)

So, here we get: P(getting at least 1 even number) = 1 -

P(not getting at least 1 even number)What does it mean to

not get at least 1 even number?

It means getting zero even numbers.

So, we can write: P(getting at least 1 even number) = 1 -

P(getting zero even numbers)P(getting zero even numbers) = P(1st coin is odd

AND 2nd coin is odd

AND 3rd coin is odd )

= P(1st coin is odd)

x P(2nd coin is odd)

x P(3rd coin is odd )

= 1/2

x 1/2

x 1/2

=

1/8So, P(getting at least 1 even number) = 1 -

1/8= 7/8

Answer: B

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Brent Hanneson – Founder of gmatprepnow.com