6

The ##n^(th)## term of a geometric sequence is generated by:

##a_n = a_”n-1″ xx r## Where r is the common ratio

In this example: ##a_0 = 4##

##a_1 = 24 = a_0 xx 6##

##a_2 = 144 = a_1 xx 6##

.. and similarly for ##a_3##

Hence: The common ratio ##r = 6##