# Density - voulme question

1. Nov 29, 2007

### poloboy

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

A balloon is to be filled with helium (density 0.178 kg/m^3) while the air outside has density 1.29kg/m^3. the mass of the empty balloon is 80kg and it is to lift a load of 240kg
what minimum volume is necessary for the lift off? assume that the balloon material and the load occupy negligible volumes.

2. Relevant equations

i am assuming that we are using P = m / V
it gives us all the necessary units to plug into this formula but my question is how do u put the 2 densities together into the equation?

3. The attempt at a solution

i think i'm suppose to use the P=m/v formula but i haven't figured out how the 2 densities are to fit together. the m = 80+240 = 320kg. can anyone point me in the right direction please.

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