Since there are two events happening simultaneously (windy and no sun), we can apply the concept of conditional probability here.
P(A|B) = P(A∩B)/P(B)
where it means that given B is happening, the probability that A is happening as well is the ratio of the chance for A and B to happen simultaneously over the chance of B to happen.
For our case, this can be interpreted as
P(A|B): it is the probability that it is windy (A) GIVEN that there is no sun (B)
P(A∩B) : chance of wind and no sun
P(B) : chance that there is no sun tomorrow
The chance of P(A∩B) is already given as 20% or 0.20. Since there is 10% or 0.10 chance of sun, then chances of having no sun tomorrow is (1-0.10) = 0.90.
Thus, we have P(A|B) = 0.2/0.9 ≈ 0.22 or 22%.
So, answer is B: 22%<span>.</span>
