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## Homework Statement

A child holding a helium filled balloon @ sea level (T= 20 C) lets go of the string. The balloon rises freely several thousand meters, where T = 5 C and P = 0.70 atm. Find the percentage change in the balloon's volume.

## Homework Equations

PV = nRT

percentage change = amount of change (amt change = V2-V1)/ original amount (V1)

## The Attempt at a Solution

Is my reasoning correct on this one? Since n and R don't change with altitude, temperature or volume, I solved for volume: V = P/T Then I solved for V1 and V2. Lastly used the above % change equation.

The only thing that is bothering me about my method is that I'm not sure how the units work out for the volume equation I posted. I guess Im figuring it jut works out (???) But, I really need to understand it for exams I see no other way to work this problem. Also- is the % change formula correct?

Thanks.