Very easy mechanics problem - am i making a stupid mistake?

[Ara macao]

An object starts at time t = 0 with a velocity of v0 = +50 m/s and undergoes a constant acceleration of a = -11 m/s^2.

b) How far from its starting (t = 0) position is the object at time t_1?

I get 44.5 meters. it sounds right 'cuz the equation would mean 0+50*1 - 11/2 *1^2 = 44.5 meters. But the computerized grading system still counts it as wrong. Am I making a stupid mistake or what?

thanks

[Doc Al]

Your answer looks OK to me. (Assuming it's straightline motion and you mean t = 1 s.) Does the system care about significant figures?