In a row of five squares, each square is to be colored either red, yellow, or blue, so that no two consecutive squares have the same color. How many ways are there to color the five squares, if there must be at least three yellow squares?
If none of the square are consecutive, then that means the yellow squares must occupy squares 1, 3, and 5.
This means only squares 2 and 4 are left to fill, with either red or blue.
We have
Blue, Blue
Red, Blue
Blue, Red
Red, Red
There sre 4 ways we can do it!
Thanks! :)