Q21. A body of mass $M$ thrown horizontally with velocity $v$ from the top of the tower of height $H$ touches the ground at a distance of 100 m from the foot of the tower. A body of mass 2 M thrown at a velocity $\frac { v } { 2 }$ from the top of the tower of height 4 H will touch the ground at a distance of $\_\_\_\_$ m .