Ball=sphere
Vsphere=pir^3
d/2=r
d=9
9/2=4.5=r
V=pi4.5^3
V=pi91.125
aprox pi=3.141592
V=286.227
round
V=286 in^3
After every month's withdrawals, 4/5 of the original amount at the start of the month will remain. The amount at the start of every month will change. Thus:
an = 4/5 (an-1) ; where a1 = 500.
It is 54 for 1 and 2 is 2520 you multply the lenght by the whith and divide by 2
