Is it always A*B =B*A? yes. 4*3= 3*4. It is elementary. The multiplication said to obey "commutative law" in math. It can be easily proved. Draw the dots as given below. 0 0 0 0 0 0 0 0 0 0 0 0 It is 4*3 matrix -(4 rows and 3 columns). Totally 12 dots. Just rotate the page by 90 degrees. We get 3*4 matrix. But the total dots are 12 only. Hence A*B=B*A. Say, you are shopping for a pair of jeans. The price is 50 dollars. But there is 20% discount. And you have to pay 8% tax also. A smart salesman may tell you "I will add the tax first and apply 20% discount on the total so that you will get more savings. Now we will do the calculation the salesman way, price 50 dollars 8% of tax 4
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