Need Help With a Physics Question (Finding Time)

Hi could someone explain to me how to solve this problem?
An arrow is fired up with an initial speed of 10 m/s. How long does it take until the arrow is at it's maximum height?

u = 10; a=-g; v=0

v=u+at

0 = 10 - 9.81 * t

t = 1.02 s

answer

The acceleration is -g, -9.8 m/s^2.

Vfinal = Vi - A*t

at the maximum height, the Vfinal = 0

0 = 10 - 9.8t