Question 156573
h = -16t^2 + 50t + 4.5
when the ball hits the ground, h will be 0
so solve the equation
-16t^2 + 50t + 4.5 = 0
solve using quadratic equation (-b +/- sqrt(b^2-4ac))/2a.

a = -16
b = 50
c = 4.5

use calculator and do not round until the end.

b^2 = 2500
4ac = 4*(-16)*4.5 = (-288)
b^2-4ac = 2500 - (-288) = 2788
sqrt(b^2-4ac) = 52.80151513

formula then becomes (-50 +/- 52.80151513) / -32

t = 3.212547345 or t = .087547348

substituting in original equation for t = 3.212547345

(-16 * 10.32046046) + (50 * 3.212547345) + 4.5 = something very close to 0.

substituting in original equation for t = .087547345

(-16 * .007) + (50 * .087) + 4.5 = something very positive so this is not the answer.  

answer is t = 3.2 seconds rounded to the nearest tenth of a second.