Maximum range of a projectile thrown at velocity v is given by
100 = v²/g
⇒ 100 = v²/9.8
⇒ v = √100×9.8
⇒ v = 31.3 m/s
With same speed, if we want to find out the maximum height, throw it vertically upward at same speed.
Maximum height = v²/2g = 31.3²/(2×9.8) = 50 m