A firecracker shoots up from a hill 160 feet high with an initial speed of 90 feet per second. Using formula H(t)= -16t^2 + vt + s approximately how long will it take the firecracker to hit the ground?

Question

A firecracker shoots up from a hill 160 feet high with an initial speed of 90 feet per second.  Using formula H(t)= -16t^2 + vt + s approximately how long will it take the firecracker to hit the ground?

anonymous · Answer

solve for $t$
$$-16t^2+90t+160=0$$

jhannybean · Answer

factor out a 16.

anonymous · Answer

Jhannybean I have and my answer is not correct.  
Satellite: I have redone that 3x and my answer is not from the chosen answers.

anonymous · Answer

anymore help??

.sam. · Answer

s will be the height as usual, v is the velocity
H(t)= 0 when it touches the ground
H(t)=-16t^2 + vt + s=0

Then 
$$-16t^2+90t+160=0$$
Solve for t

.sam. · Answer

Did you use quadratic formula?

.sam. · Answer

$$t=\frac{-90 \pm \sqrt{90^2-4(-16)(160)}}{2(-16)}$$

anonymous · Answer

yes.  I have had to move on.  I cant get the correct answer.  Thank you so much.

jhannybean · Answer

You would have had two answers for t, one solving for [-b + sqrt{b^2-4(a)(c)}]/2a and the other one for [-b-sqrt{b^2-4ac}]/2a