Calculating truck speed in collision with a tree | Physics problem solution

[Steveku]

Question:
The driver of a truck slams on the brakes when he sees a tree blocking the road. The truck slows down uniformly with an acceleration of -5.60 m/s2 for 4.20 s, making skid marks 62.4 m long that end at the tree. With what speed does the truck then strike the tree?

Conclusion:
equation: dx = volt + .5at^2
62.4 m = v (4.20s) + .5 (-5.60 m/s^2) (4.20s)
v=26.6 m/s

May you experts please check if this is correct? Thanks a bunch.

 

[malawi_glenn]

is volt the initial velocity*time ?

if so is the case, you only calculated the initial speed of the truck.

v=vo + at