Techniques of Integration · Hard problem

A $1$ kg ball is dropped and falls under gravity ($g=10$ m/s$^2$) through air whose resistance is $0.1v^2$ N, so its downward velocity satisfies $\dfrac{dv}{dt}=10-0.1v^2$, $v(0)=0$. Find the time $t$ (in seconds) at which $v=6$ m/s.