I don't understand why my final velocity is wrong on this incline question.

Question

A can of soup travels down an inclined plane which is 3.00 m long and makes an angle of 25 degrees with the horizontal. It travels this distance in 1.50 seconds. What is the final velocity, assuming the can of soup started at rest, a perfect roll is occurring, and friction is negligible?

I have solved the answer below. What I do not understand is why is my answer wrong? It seems that the acceleration is what is wrong, but I don't understand why.

I used the formulas:

(vf+vi)/2=vavg

vf^2=vi^2+2*a*s

a=gsin(theta)

Solution:

a = 9.8*sin(25*pi/180)=>a=4.1417 m/s^2

vf^2=vi^2+2*a*s=>vf=sqrt(0^2+2*4.1417*3)=>vf=4.9850 m/s

Meanwhile the correct answer is:

(vf+vi)/2=>(vf+0)/2=2=>vf=4 m/s

Answer 1

I think that right answer is 4m/s: v/2·t = l; v = 2l/t = 2·3m/1.5s = 4m/s

Because they not specify if no other forces, for example resistance.