Question

The mass of air displaced by balloon is $X$ kg. Find $\frac{X}{3}$

• A. 5.6
• B. 6.5
• C. 7.5
• D. None of these

Answer 1

The correct option is B 6.5

The mass of a body is calculated from the formula, $Mass=Density\times Volume$.
The volume of the balloon is the volume of hydrogen that will be present in the balloon. So the volume of air that would be displaced will also be the same, that is, $15m^3$. The density of air is $1.3kg/m^3$.
Therefore, the mass of the air displaced = $15\times 1.3=19.5kg=X$. So, $\frac{X}{3}=6.5kg$.
Hence, the value of x is 6.5 kg.