1. The problem statement, all variables and given/known data The lengths a,b,c of a rectangle are changing with time. At the instant in question, a=1m, b=2m, c=3m and da/dt = db/dt = 1m/sec, and dc/dt = -3m/sec. At what rate is the box's volume changing at this instant? 2. Relevant equations Chain rule for partial derivatives. 3. The attempt at a solution ∂V/∂t=(bc)(da/dt)+(ac)(db/dt)+(ab)(dc/dt) Substituting the values gives 3m^3/s. Am I right? Thanks for helping me out. The answer is not given in the book.