An object is dropped from a height of 1,600 feet. the amount of time, in seconds, the object takes to hit the ground can be found by solving the equation −16t2+1,600=0. how many seconds will it take to hit the ground?

As it is stated in this item, in order to determine the amount of time it takes to hit the ground, the equation 
                           -16t² + 1600 = 0

Transpose the terms without variable to the other side of the equation,
                             -16t² = -1600

Divide the equation by -16.
                               t² = 100

Solve the value of t by getting the square root of the equation.
                               t = +/- 10

Thus, it will take the object 10 seconds to reach the ground.