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!
To find all of the feet of pipe that Brad has, you add both of the lengths of the pipes together. So 2 5/12+3 7/12. Add the numbers together first, 5. Then add the fractions, 5/12+7/12=1. So add 5 and 1 and you get 6 feet of pipe. Hope this helps.
