Subject: probability and odds
Question: the chances of rain on friday, saturday, and sunday are 20%, 30%, and 50% respectively. what are the odds it will rain all three days?
The probability that it rains on Friday is 20% so the probability that it doesn't rain is 80%. The ratio 20:80 is called the odds that it rains on Friday. Since it is a ratio I could equally well have written 2:8 or 1:4.