A 17.5 m high waterfall launches water horizontally. The water hits the gound 2.5 meters from the base of the waterfall how many seconds does the water take to reach the ground

The question actually can't be answered that way.

If the water starts falling 17.5 meters above the ground (AND this is all happening on Earth), then it hits the ground  1.89 seconds later.  

If it also had some initial horizontal speed, that ould  have no effect on the time it takes to reach the ground.  Only gravity does.

If the water hit the gound 2.5 meters from the base, then it must have shot horizontally off the cliff at (2.5m / 1.89 sec)  =  1.32 m/s .

If THAT (horizontal) speed was different, then the water would have hit the ground at some OTHER distance from the base, after falling for 1.89 sec.

the answer is 12 as i may remember

: )