To solve this problem it is necessary to apply the concepts related to the kinematic equations of motion for which the height of a particle is defined as a function of gravity as,
[tex]v^2 = 2gh[/tex]
Where,
h = Height
g = Gravity constant
v = Velocity
There is not change in the horizontal component, therefore there is only the component horizontal given (18m/s) and the vertical component:
[tex]v^2=2*g*h[/tex]
[tex]v^2=2*9.8*16[/tex]
[tex]v=17.70 m/s[/tex]
Applying the vector theory to find the magnitude of a vector we have to
[tex]|\vec{V}| = \sqrt{17.7^2+18^2}[/tex]
[tex]|\vec{V}| = 25.38m/s[/tex]
The speed at which the ball was thrown was 25.38