1. The problem statement, all variables and given/known data A 0.900 g balloon is filled with helium gas until it becomes a 25.0 cm-diameter sphere. What maximum mass can be tied to the balloon (with a massless string) without the balloon sinking to the floor? 2. Relevant equations Fb=VSphere*Pair*Gravity Fg=Vsphere*Phelium*Gravity 3. The attempt at a solution I tried to set them equal to each other (so that the net force is 0) and found that... Vsphere(Phelium-Pair)*9.8-0.0009kg*9.8(mass of ballon)=Mass attachable/9.8 I got 7.5g but that's wrong. Anyone know where I messed up my process?