Calculating Mass of Helium in a Balloon

[titanium90]

Homework Statement

A balloon 20 m in diameter is filled with helium at a gauge pressure of 2.0 atm. A man is standing in a basket suspended from the bottom of the balloon. A restraining cable attached to the basket keeps the balloon from rising. The balloon (not including the gas it contains), the basket and the man have a combined mass of 150 kg. the temperature is 24oC that day and the barometer reads 760 mm Hg.

What is the mass of helium?

Homework Equations

pV = nRT

The Attempt at a Solution

(3 atm x 101325 Pa/atm)(4/3*pi*(10^3)) = (m/0.004)(8.314)(297.15)
m = 2061 kg

But the correct ans is 2050 kg. Anyone pls help? thanks

 

[phinds]

Well, your math is right so if your constants are right then you have the right answer.