To start with solving this problem, let us assume a launch angle of 45 degrees since that gives out the maximum range for given initial speed. Also assuming that it was launched at ground level since no initial height was given. Using g = 9.8 m/s^2, the initial velocity is calculated using the formula:
(v sinθ)^2 = (v0 sinθ)^2 – 2 g d
where v is final velocity = 0 at the peak, v0 is the initial velocity, d is distance = 11 m
Rearranging to find for v0:
v0 = sqrt (d * g/ sin(2 θ))
v0 = 10.383 m/s