Sometimes nobody timed anything. You have a starting speed, a finishing speed, an acceleration and a distance — and not one second between them. For exactly that case there is $v^2 = v_0^2 + 2ad$, read v squared equals v-nought squared plus two a d. The cast, once more: $v$ is the final velocity in m/s, $v_0$ the initial velocity in m/s, $a$ the acceleration in $\mathrm{m/s^2}$, $d$ the displacement in metres. No $t$ anywhere, by construction — it is what you get when you solve $v = v_0 + at$ for t and substitute it into the position function. The clock cancels itself out on the way through.

The square is the physics, not the algebra. Because speed enters SQUARED, doubling a vehicle's speed quadruples the distance it needs to stop — the single most useful fact any driver ever learns from a mathematics class. Whenever you meet a v² relation, expect the consequences to be steeper than they feel.

Two slips live here and both are worth naming out loud. One: forgetting to square $v_0$ — it is squared on the right just as surely as v is on the left. Two: forgetting to take the root at the end. This relation hands you $v^2$, a number wearing $\mathrm{m^2/s^2}$, and a speed is not a speed until the root has run. Check the units of what you are about to write down; if they are squared, you are not finished.