Solving the Puzzle: Ball Thrown Upward

[iluvpandas]

Homework Statement

A ball is thrown straight up with an initial speed of 40 m/s. (Neglect air resistance.)
How high does it go? how long does it stay i the air

Homework Equations

i know the second part is 8 because its basically saying 40m every second divide by acc.(gravity) which is basically 10 and multiply by 2 one second going up and another going down. but I am completely lost on the first part

The Attempt at a Solution

im not sure but i think i use the formula for displacement? but when i tried the answer was wrong.

 

[rootX]

Write the three motion equations here. And then see what you are looking for.
What is the final velocity?
What is initial velocity?
What is distance? - not known
What is time? - not given
What is acceleration?

You should try equation with time in it when finding the distance.