Question

A ball is thrown upward with an initial velocity of 27 m/s. How long is the ball in the air?

Answer 1

use equation of motion:
\[v = u + at\]

for the upward journey
\[a = -9.8 \ m/s^2\]
\[u = 27 \ m/s\]
\[v = 0 \ m/s\]

solve for t, that's how long it takes to get to top of its upwards journey

but you want 2 x t as it has to drop back again