For the past four weeks Micah has been recording the daily high temperature. During that time the high temperature has been greater than 45'f on 20out of 28 days. What is the experimental probability that the high temperature will be below 45'f on the 29 day

The experimental probability of it being greater than 45°F is

P (greater than 45°F) = 20/28

which can be simplified to 5/7.

The probability of something not happening is

1 - probability of that something happening

So P (less than 45°F) = 1 - P (greater than 45°F)

(assuming that 45°F is included with the greater than)

So the experimental probability of it NOT being greater than 45°F is therefore

P (less than 45°F) = 1 - 5/7

If we want to simplify and write as a single fraction, write 1 as 7/7 so that we have a common denominator. Then

P (less than 45°F) = 7/7 - 5/7

= 2/7

The experimental probability that the high temperature will be below 45°F on the 29th day is 2/7.