L=T2xg/4x3.14^2
16x9.8/4x3.14^2
Used your calculator plz
Kinetic energy is calculated by using formula:
Ek = 1/2*m*v^2
Now we replace values of mass and speed in this formula.
Ek = 1/2*10*3^2 = 45.0J
When you have a formula and all variable values are given in the text of question just replace variable values in equation and find the final value.
Answer:
v = 44,16 m/s
Explanation:
We will fixate our reference in the starting point from where Dan jumped of, at the top of the Casino. Therefore, the displacement made when dan reached the airbag would be of y= -99,4 m viewed from our reference. We describe the motion of dan with the equation:

Dan jumped from the rest, that means that the initial velocity v_0=0, therefore:

Since Dan is moving in the negative axis regarding our reference point, we take the negative root of the equation.
v_y=-√(2*(-9,81 m/s^2 )*(-99,4 m) )=44,1613 m/s 
So, if we don’t take the air resistance into account, Dan would have achieved an velocity of 44,16 m/s when he reached the airbag.
I hope everything was clear with my explanation. If you need anything else, let me know. Have a great day :D