Hello there. To solve this question, we'll simply have to take the ratio between the heights the ball has reached.
Given that the lacrosse ball was dropped from a height of 120 cm and it rebounds to a height of 78 cm, we want to find the rebound ratio.
In this case, the rebound ratio will be the height the ball reached after the bounce and the height it was dropped from:
Rebound ratio 78 : 120
Simplify the numbers by a factor of 2
Rebound ratio 39 : 60
This is the ratio we've been looking for.