To solve this we are going to use the formula for the volume of a sphere: 
where
is the radius of the sphere
Remember that the radius of a sphere is half its diameter; since the first radius of our sphere is 24 cm,
. Lets replace that in our formula:
Now, the second diameter of our sphere is 36, so its radius will be:
. Lets replace that value in our formula one more time:
To find the volume of the additional helium, we are going to subtract the volumes:
Volume of helium=
We can conclude that the volume of additional helium in the balloon is approximately <span>17,194 cm³.</span>
where
Remember that the radius of a sphere is half its diameter; since the first radius of our sphere is 24 cm,
Now, the second diameter of our sphere is 36, so its radius will be:
To find the volume of the additional helium, we are going to subtract the volumes:
Volume of helium=
We can conclude that the volume of additional helium in the balloon is approximately <span>17,194 cm³.</span>