Question

If $P$, $Q$, $R$ are physical quantities, having different dimensions, which of the following combinations can never be a meaningful quantity ?

• A. $\frac{\left(P-Q\right)}{R}$
• B. $PQ -R$
• C. $\frac{PQ}{R}$
• D. $\frac{\left(PR-Q^{2}\right)}{R}$

Answer 1

Answer: (A)

Physical quantities having different dimensions cannot be added or subtracted.
As P, Q and R are physical quantities having different dimensions, therefore they can neither be added nor be subtracted. Thus, (a) can never be a meaningful quantity.