V is inversely proportional to the square root of m and m is inversly proportional to the square of t. The relationship between V and t is
$$V \propto \frac{1}{\sqrt{m}}$$
$$m \propto \frac{1}{t^2}$$
Now,ย
$$V \propto \frac{1}{\sqrt{\frac{1}{t^2}}}$$
$$V \propto t$$