Question

If A is of order p × q and B is of order q × r what is the order of AB and BA?

Answer 1

If A is of order p × q .....[∵ p × q q × r = p × r]
the order of AB = p × r .......[∵ q × r p × q = r ≠ p]
Product of BA cannot be defined/found as the number of columns in B ≠. The number of rows in A.