Question #f8cb8

1 Answer
Oct 5, 2016

It depends on the question asked and which operation you are doing.


The operation you need to do depends on the probability question asked.

If there is an indication of several outcomes combined, the probabilities are multiplied. This is indicated by "AND"

for example:
Probability that the the wind is blowing #7/9# AND the kite flies #3/5# AND it sticks in a tree#1/3#. All 3 events must happen.

Three probabilities would be multiplied together - that means the numerators and the denominators.
#7/9 xx3/5 xx1/3 = (7xx3xx1)/(9xx5xx3)#

If there is an indication of a choice, then the probabilities have to be added. This is indicated by OR

for example
Probability that Anne takes a pear #3/10# OR a banana #5/10#from the bowl, - only one of the events happens

In this case the probabilities are added, which means you need to find a common denominator, make equivalent fractions, and then only add the numerators, keeping the same denominator.

#3/10+5/10 = 8/10 = 4/5#