# If the probability that an event will happen is 0.31, what is the probability of the event's complement?

Feb 17, 2018

$0.69$

#### Explanation:

the complement is the probability that an event will not happen.

since the total probability is $1$, the probability of an event happening, added to the probability of its complement, is always $1$.

the probability of the complement can be found by subtracting the probability of the event from $1$.

$1.00 - 0.31 = 0.69$

$0.69 + 0.31 = 1$
P(event) + P(complement) $= 1$

the probability of the complement is $0.69$.