To find the mass of helium in the balloon, you can use the formula:
\[ \text{mass} = \text{volume} \times \text{density} \]
Given that the volume of the helium is 2,850 cubic meters and the density is 0.1685 kilograms per cubic meter, we can calculate the mass as follows:
\[ \text{mass} = 2,850 , \text{m}^3 \times 0.1685 , \text{kg/m}^3 \]
Now, performing the multiplication:
\[ \text{mass} = 2,850 \times 0.1685 = 480.225 , \text{kg} \]
Rounding this to the nearest whole number gives:
\[ \text{mass} \approx 480 , \text{kg} \]
So, the answer is:
480