A balloon has a diameter of 10 inches and a height of 20 inches. How much helium will it take to fill the balloon in inches cubed
Helium needed = Volume of the balloon
Now, since you've given two different measurements, I presume the balloon is in the shape of an ellipsoid.
For an ellipsoid,
V = (4/3)π(a)(b)(c),
Where a, b, and c are the axes of the ellipsoid.
In this case, a = h/2 = 10 inches
b = c = d/2 = 5 inches
V = (4/3)*π*10*10*5
= 1047.2
You need 1047.2 inches cubed of helium.