In case you need to find probability of happening of two independent events we use multiplication theorem.
P(AB) = P(A) * P(B)
Lets understand this theorem with help of an example
Question – An unbiased coin is tossed twice. Find the probability of getting 1,2,3 or in the first toss and 4,5 or 6 in second attempt ?
Probability of getting 1,2,3 or 4 in first toss = 4/6 = 2/3
Probability of getting 4,5 or 6 in second toss = 3/6 = 1/2
Now both events are independent and we will use multiplication theorem
1/2 * 2/3 = 1/3