How do you find the speed of kenetic energy

Kinetic energy of a moving object =  (1/2 of the mass) x (speed²) .

Divide each side by (1/2 of the mass)
and you get:

                                   Speed²  =  (KE) / (1/2 of the mass)

Take the square root
of each side:                  Speed = √ (2 · KE / mass) .

That's what you need, right there.

If you know the kinetic energy, then ...

-- double it,

-- divide by the object's mass,

-- take the square root.

Now you have the object's speed.

Kinetic energy = 1/2mv^2. since the mass is constant we can form a ratio of it's kinetic energy at 60 divided by that at 30 to see ke(60)/ke(30) = +(60^2)/30^2). this may be said to 300% increase.

The answer is a.  i hope this