```Question 174626
5) Crossing a wooden bridge at Letchworth Park, Melissa drops a penny into the water below for good luck. If the height of the penny is modeled by the function h(t)=64 - 16t^2, where t represents time in seconds and h(t) is height in feet, how many seconds did it take the penny to hit the water?
(a) 1 (b) 2 (c) 3 (d) 4

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Let h(t) = 0

0 = 64 - 16t^2

All you have to do is solve for t.

Can you take it from here?

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Here is one of your questions:

(5) Crossing a wooden bridge at Letchworth Park, Melissa drops a penny into the water below for good luck. If the height of the penny is modeled by the function h(t)=64 - 16t^2, where t represents time in seconds and h(t) is height in feet, how many seconds did it take the penny to hit the water?
(a) 1 (b) 2 (c) 3 (d) 4

Let h(t) = 0

0 = 64 - 16t^2

Subtract 64 from both sides.

-64 = -16t^2

Now divide both sides by -16.

-64/-16 = t^2

64/16 = t^2

4 = t^2

Finally take the square root of both sides of the equation.

sqrt{4} = sqrt{t^2}

2 = t