A abd B are the only two outcomes of an event probability of A is 0.9 then what will be the probability of B

Break Down the Problem

1. Identify the two outcomes of the event, which are A and B.
2. Understand that the sum of the probabilities of all possible outcomes must equal 1.

Relevant Concepts

1. Probability of an event A is given as $P(A) = 0.9$.
2. The total probability for all outcomes in a sample space is given by: $P(A) + P(B) = 1$
3. Therefore, to find $P(B)$: $P(B) = 1 - P(A)$

Analysis and Detail

1. Substitute the known value of $P(A)$ into the equation: $P(B) = 1 - 0.9$
2. Perform the calculation: $P(B) = 0.1$

Verify and Summarize

1. The calculations check out, as both probabilities sum to 1: $P(A) + P(B) = 0.9 + 0.1 = 1$

Final Answer

The probability of B is $P(B) = 0.1$.