Question

Sean tossed a coin off a bridge into the stream below. The path of the coin can be represented by the equation h = -16t2 + 72t + 100. How long will it take the coin to reach the stream?

Answer 1

about 5.613 seconds

Explanation:

Using the quadratic formula to find the value of t when h = 0, we have ...

at² +bt +c = 0

t = (-b±√(b²-4ac))/(2a)

t = (-72±√(72² -4(-16)(100)))/(2(-16))

t = (-72±√11584)/-32 = (9±√181)/4

Only the positive value of t is of interest.

The coin will hit the stream after (9+√181)/4 seconds ≈ 5.613 seconds.