Question 588640
<pre>
Odds in favor = successes:failures


Odds against = failures:successes

Probability of success = {{{successes/(successes+failures)}}}

Probability of failure = {{{failures/(successes+failures)}}}

You have the odds in favor of snow tomorrow as 3:5.

So "it will snow tomorrow" is considered a SUCCESS and 
"it will NOT snow tomorrow" is considered a FAILURE.

Therefore successes = 3 and failures = 5

The probability that it will NOT snow tomorrow is the probability of a failure:

Probability of failure = {{{failures/(successes+failures)}}} = {{{5/(3+5)}}} = {{{5/8}}}

Edwin</pre>