# calculus

a parachutist falling at the rate of 15 ft./sec. drops a stone. if he was 904 ft. above the ground when the stone was dropped, how long would it take the stone to reach the ground?

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1. assuming a = -32
and seeing that the initial velocity was -15 from a height of 904, I know

s = -16r^2 - 15t + 904
we want s = 0

16t^2 + 15t - 904 = 0
won't waste time trying to factor it ...
t = (-15 ± √58081)/32
= (-15 ± 241)/32 ----- ahh, it does factor
= 226/32 or some silly negative
= 113/16 seconds or appr 7.1 seconds

btw, it would have been factored as
(16t - 113)(t + 8) = 0

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2. Thank you. You’re so helpful.

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