**Problem Analysis**

To find the velocity of rain experienced by a person standing on the ground, we need to consider the vertical velocity of rain and the horizontal velocity of the wind.

**Given Data**

Vertical velocity of rain (v_rain) = 25√3 m/s (downwards)
Horizontal velocity of wind (v_wind) = 25 m/s (eastwards)

**Solution**

To find the velocity of rain experienced by a person standing on the ground, we need to combine the vertical and horizontal velocities using vector addition.

**Vertical Velocity of Rain**

The vertical velocity of rain is given as 25√3 m/s (downwards). Since the rain is falling vertically, there is no horizontal component of velocity in the vertical direction. Therefore, the vertical velocity of rain (v_rain_y) = 25√3 m/s.

**Horizontal Velocity of Wind**

The horizontal velocity of the wind is given as 25 m/s (eastwards). Since the person is standing on the ground, there is no vertical component of velocity in the horizontal direction. Therefore, the horizontal velocity of wind (v_wind_x) = 25 m/s.

**Combined Velocity of Rain**

To find the combined velocity of rain, we need to add the vertical and horizontal components of velocity. Since the rain is falling vertically downwards and the wind is blowing horizontally eastwards, the combined velocity of rain (v_combined) can be found using the Pythagorean theorem:

v_combined = √(v_rain_y^2 + v_wind_x^2)

Substituting the given values:

v_combined = √((25√3)^2 + 25^2)

Simplifying:

v_combined = √(1875 + 625)

v_combined = √2500

v_combined = 50 m/s

Therefore, the velocity of rain experienced by a person standing on the ground is 50 m/s.