Question

I got everything else right but this one i don't get help please?

The function y = –16t2 + 224 models the height y in feet of a stone t seconds after it is dropped from the edge of a vertical cliff. How long will it take the stone to hit the ground? Round to the nearest hundredth of a second. (1 point)

0.25 seconds
5.29 seconds
7.48 seconds
3.74 seconds

Answer 1

Just work out when y = 0 it's easy, so start with 0 = -16t2 +224
-224 = -16t2 negatives cancel out
224 = 16t2
224/16 = t2
14 = t2
t = 3.74

Answer 2

If you can't work it out you can always use wolfram http://www.wolframalpha.com/input/?i=+y+%3D+%E2%80%9316t2+%2B+224

Answer 3

The function y = –16t2 + 224 models the height y in feet of a stone t seconds after it is dropped from the edge of a vertical cliff. How long will it take the stone to hit the ground? Round to the nearest hundredth of a second. (1 point)
(0 pts) 0.25 seconds
(0 pts) 5.29 seconds
(0 pts) 7.48 seconds
(1 pt) 3.74 seconds
1 /1 point