60/40 = 1.5 So Renee will need to drive 40miles 1.5 times in order to
cover 60 miles.
Since her speed is exactly 40 mph, she'll need to keep it up for <em>1.5 hours</em>.
First answer is the fourth one, 2 and 6
When the firecracker hits the ground, H(t) = 0.0 = -16t^2 + 90t + 160 Using 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.
Seven Seconds is your answer!