Do Dimensional Analysis.
Dimensional analysis helps you to check your formula derivation. All terms in the equation should have the same dimension ( or units)
Example: The pressure p is defined as the force F per unit area A. Suppose you measure force in Newton N and length in m. What is the unit of pressure?
P = F/A. Since the dimension of A is length2. Thus pressure is measured in N/m2 .
Example: Which of the following formula has correct dimension?
Answer: v = x / t.