what formula to use or how to solve this problem?

Question

diver leavs a 10 m platform with forward horizontal velocity of 1 m/s and upward vertical velocity of 4 m/s. what is horizontal, vertical and resultant velocities of diver 0.25 s after she leaves the platform.

Answer 1

the velocity due to the accelaration ( ' gravity ' ) is time x 9.8 meter / sec^2

initial horizontal speed remains the same : 1 m/s,
vertical velocity is 4 + 9.8 x 0.25 seconds ( is assume the diver dives down ) if dive is up it is 9.8 x 0.25 - 4