math
posted by pie .
A spherical water tank has a diameter of 10 feet. How much water does it hold when half full? (Use 3.14 for p)

the formula for the volume of a sphere is (4/3)pie r^3
So, (4/3) * 3.14 * r^3
to find the radius, divide the diameter by 2, so it has a readius of 5 ft
Now, plug in the numbers to the formula and solve. That is the answer for the volume of that sphere. NOW, you want to know what it is when 1/2 full, so just divide by 2 to get your answer for this problem 
P.S.  remember order of operatins when solving! :)