Arock is dropped from a bridge 320 feet above the river. the pathway that the rock takes can be modeled by the equation h= -16t2+320. how long will it take the rock to reach the river?

4.47 seconds.

Step-by-step explanation:

Hi, the rock will reach the river when the height (h) is 0.

So, replacing in the equation given:

h= -16t2+320

Where t is the time  

0= -16t2+320

Solving for t

-320 = -16t2

-320/-16 =t2

20 = t2

√20 =t

4.47 = t

Assuming that t is the time in seconds, the rock will reach the river after 4.47 seconds.

Feel free to ask for more if needed or if you did not understand something.