Calculating Velocity of a Rocket: Balancing Mass and Velocity

[lasha1]

To calculate velocity of the rocket: v1=m2/m1 × v2 where v1 and m1 is mass and velocity of rocket and v2 and m2 is the mass and velocity of fuel.
Problem: m1 is saying that you have to decrease the mass of the rocket and increase the mass of fuel. But if you decrease the mass of rocket, the mass of fuel automatically deacrease.
How this situation works. I mean how to choose masses

 

[Merlin3189]

I'm not sure where you're getting this equation from, nor even what your symbols mean. Is v1 really Δv, the change in velocity? Does m1 include m2? Or is the total rocket mass really m1+m2 at the start and m1 when the fuel is spent?

I think you need to look up rocket equation and sort it out before you try to draw any conclusions about it.