The chromatic number of the following graph is

Q. The chromatic number of the following graph is 

Ans: 3

Sol:

Chromatic number of given graph is 3.

Note that graph is Planar so Chromatic number should be less than or equal to 4 and can not be less than 3 because of odd length cycle. In other words if a graph is planar and has odd length cycle then Chromatic number can be either 3 or 4 only.