Answer:
0.216 has exactly one cube root, which is 0.6.
Explanation:
Note that the third root of 0.216 is 0.6, obtained on a calculator by typing in 0.216^(1/3). Verify this root by cubing 0.6: 0.6*0.6*0.6 = 0.216. Thus, 0.216 has exactly one cube root.