So given [tex]d=5t^2[/tex], you need to substitute 2t as t, [tex]5(2t)^2[/tex]. Simplify the equation; [tex]5(4t^2)[/tex] and then to [tex]20t^2[/tex]. when you plug in values for time, lets say 4, the distance traveled quadruples.
[tex]d=5(4)^2[/tex]
[tex]d=80m[/tex]
[tex]d=5(20)^2[/tex]
[tex]d=320m[/tex]