Answer:
1.25 m
Step-by-step explanation:
Constant Acceleration Equations (SUVAT)

When using SUVAT, assume the object is modeled as a particle and that acceleration is constant.
Consider the horizontal and vertical motion of the ball separately.
As the ball rolls off the table with a horizontal velocity only, the vertical component of its initial velocity is zero.
Acceleration due to gravity = 10 ms⁻²
As we need to find the vertical displacement of the ball, resolve vertically, taking ↓ as positive:


Therefore, the vertical displacement of the ball is 1.25 m, and so the table is 1.25 m above the floor.