algebra
posted by John on .
find all the real cube roots of 0.000216
a) 0.0036
b) 0.06
c) 0.0036 and 0.0036
d) 0.06 and 0.06
multiple choice

Well, it has to be negative, say a if a is a positive number
because (a)(a)(a) = a^3
but
a*a*a = +a
so that deletes options a) and c) and d)
which leaves us with b)
try b)
(.06)(.06)(.06) = .000216
sure enough, b) works
I bet the other two roots are complex conjugates :)