Carcass 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
_________________
Brent Hanneson - founder of Greenlight Test Prep