GreenlightTestPrep wrote:
huda wrote:
There is an 80% chance David will eat a healthy breakfast and a 25% chance that it will rain. If these events are independent, what is the probability that David will eat a healthy breakfast OR that it will rain?
(A) 20%
(B) 80%
(C) 85%
(D) 95%
(E) 105%
P(A or B) = P(A) + P(B) - P(A and B)So, P(healthy breakfast OR rain) = P(healthy breakfast) + P(rain) - P(healthy breakfast AND rain)
Note: since P(healthy breakfast) and P(rain) are INDEPENDENT, P(healthy breakfast AND rain) = P(healthy breakfast) x P(rain)
= 0.8 x 0.25
=
0.2So, P(healthy breakfast OR rain) = P(healthy breakfast) + P(rain) - P(
healthy breakfast AND rain) = 0.8 + 0.25 -
0.2 = 0.85
Answer: C
Cheers,
Brent
I have a little bit confusion here, before shed some light on my confusion i want to say that,i watched your video related this topic (mutually exclusive, dependent and independent events).
We use this formula when Both Events are mutually exclusive ---First One: P(A or B) = P(A) + P(B), and
When they are not mutually exclusive ----- Second One: P(A or B) = P(A) + P(B) - P(A and B)
NOw above question both event are there mutually exclusive so as rules we need to follow the 1st one but why we used the 2nd one?