A firecracker shoots up from a hill 160 feet high with an initial speed of 90 feet per second. Using the formula H (t) = - 16t2 + vt + s, approximately how long will it take the firecracker to hit the ground? ... ?

When the firecracker hits the ground, H (t) = 0.0 = - 16t^2 + 90t + 160Using the quadratic formula, t = (-90 + - sqrt (90^2 - 4 (-16) (160))) / 2 (-16) t = - 1.42 ort = 7.04

The negative time is extraneous. Therefore, t = 7.04 s.