How do i solve 89 times 69

B

Step-by-step explanation:

The trick you need to employ is that when the rock hits the ground, the timer stops. So h must be taken as 0.

0 = - 16t^2 + 255            Set up the equation

- 255 = - 16t^2                Divide by -16

15.9375 = t^2                  Switch

t^2 = 15.9375                   Take the square root of both sides.

sqrt(t^2) = sqrt(15.9375)

t = 3.992 seconds

The closest answer is B