Bijesh wrote:
Probability of a couple having a boy child is 0.4. If a couple decides to have 3 children, what is the probability that at least one of them is a girl child?
A) 0.064
B) 0.64
C) 0.36
D) 0.936
E) 1
We want P(select at least 1 girl)
When it comes to probability questions involving "
at least," it's 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 girl) = 1 -
P(not getting at least 1 girl)What does it mean to
not get at least 1 girl? It means getting zero girls.
So, we can write: P(getting at least 1 girl) = 1 -
P(getting zero girls)P(getting zero girls)P(getting zero girls) = P(getting 3 boys)
= P(1st child is boy
AND 2nd child is boy
AND 3rd child is boy)
= P(1st child is boy)
x P(2nd child is boy)
x P(3rd child is boy)
= 0.4
x 0.4
x 0.4
=
0.064So, P(getting at least 1 girl) = 1 -
0.064= 0.936
Answer: D
Cheers,
Brent