Volume of a sphere formula is: V=4 /3 πr^3
You know v=17000 and pi=3.14
17 000 = 4/3 x 3.14 x r^3
(divide 17 000 by 4/3 x 3.14 ) --> r^3 = 4060.51 (2dp)
(cube root is to get just r) r = 15.95 inches (2dp)
There 15 inches to the nearest inch.
Hope this is correct! :D