Hi,

I am having trouble with the following question:

During winter it rains on average 18 out of 30 days. Five winter days are selected at random. Find (4 d.p) the probability that:

(a) the first two days chosen will be fine and the remainder wet

My approach is this is an ordered selection:

I have defined p = it will rain =

or 0.6

q = 1 - 0.6 = 0.4

=

= 0.03456

.... Looks right to me
The answers I have are yielding 0.0124.

(b) more rainy days than fine days have been chosen

P(3 rainy days) =

P(4 rainy days) =

P(5 rainy days) =

= 0.3456 + 0.2592 + 0.007776

..... 0.07776
= 0.612576

...... 0.68256
The answers are yielding 0.7102

I wonder where I am going wrong

TIA for any assistance!