[math]t'=\frac{t}{\sqrt{1-\frac{V^2}{c^2}}}[/math]
[math]m'=\frac{m}{\sqrt{1-\frac{V^2}{c^2}}}[/math]
try it out for yourself. plug in any value for mass or time and velocity. mass prime or time prime will be the mass or time at that speed.
it may be fun to put your own mass in the equation to see your mass at different velocities. in case you don't know, to get your mass, divide your weight by [math]9.81\frac{m}{s^2}[/math]. if you are using the english system divide your weight by [math]32.2\frac{ft}{s^2}[/math].