In the following question, a matrix of certain characters is given. These characters follow a certain trend, row-wise or column-wise. Find out this trend and choose the missing character accordingly.
7 9 21 27
4 2 36 18
9 4 54 ?

Answer: B. 24

In the first row, 7 x 3 = 21,  9 x 3 = 27.
In the second row, 4 x 9 = 36,  2 x 9 = 18.
In the third row, 9 x 6 = 54.
.'. Missing number = 4 x 6 = 24.