Note that the half life is 22 years, and that 50% of the original amount is left after that number of years. 88 years is 4 times the half life, and so the amount left after 4(22), or 88, years is 6.25%. Note that the Pb-210 continues to decay.
By calculus or elementary geometry, we know that the formula for the volume of a cone, given pi (the constant), its height h and its radius r is: Lets solve this relation for the radius: Now we have found a general formula that gives us the radius of a cone, given its volume and height. We need only substitute height (20in) and pi=3.14 to get the numerical equation: r=0.2185*