Algebra II
posted by Emily on .
7. How many different signals can be made by displaying six flags, all at a time, on a flagpole, if three are white, one blue, one red, and one yellow?
 Here, I thought you could to 6! to equal 720 possible combinations, but my teacher marked this problem wrong.
14. Two dice are rolled. What is the probability that either the sum of the numbers showing is 7 or both numbers are even?
 I do not understand how to do this problem at all :(

Can someone help me with these problems? Any help is greatly appreciated :) thanks!!

7) 6!/3!= 120

There are 6 ways to get a 7
there are 9 ways to have both even
these are mutually exclusive events, that is, you can't have a sum of 7 AND both be even
so Prob(a sum of seven OR both are even)
= 16/36 = 4/9
or by formula
Prob(sum of seven OR both even)
= Prob(sum of seven) + prob(both even)  prob(sum of seven AND both even)
= 6/36 + 9/36  0
= 4/9 
Ooooohhhhh I totally get it now!! Thanks anonymous and Reiny :)