Differentiating the Integral Form of the Continuity Equation for Fluids

1. The problem statement, all variables and given/known data

I am working on a problem that asks to use the integral form of the continuity equation (for a steady flow) and show that it can equal this (by taking the derivative of it): dr/r + dV/V + dA/A = 0 where V is Velocity and r is the density.

2. Relevant equations

What would the derivative be with respect to?

3. The attempt at a solution

I was able to bring it down to: rVA=0 but I am unaware how to differentiate this so that it looks like the equation above.

Thanks.

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 Never mind... I have forgotten the old chain rule from calculus. I was over thinking this problem.

 Tags aerodynamics, continuity, fluid dynamics, fluid mechanics, mass conservation