Two quantities A and B have different dimensions. Which mathematical operation given below is physically meaningful? [PMT/NEET-1997]
a. $A/B$
b. $A + B$
c. $A – B$
d. None

Solution

• Addition and subtraction are possible only if physical quantities have the same dimensions.
• If $A$ and $B$ have different dimensions, $A+B$ or $A-B$ are meaningless.
• Division or multiplication of quantities with different dimensions is allowed.

So, $A/B$ is physically meaningful.

Answer
a. $A/B$