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  3.856 seconds

Step-by-step explanation:

Set d=10 and solve for t.

  10 = -12t^2 -3t +200

  12t^2 +3t -190 = 0 . . . . . . subtract the expression on the right to put into standard form

This is a quadratic equation, so the quadratic formula can be used to find solutions. That formula tells you the solution to ...

  ax^2 +bx +c = 0

is

  x = (-b ±√(b² -4ac))/(2a)

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We have a=12, b=3, and c=-190. The variable in our equation is t, not x. Putting these values into the formula, we find ...

  t = (-3 ±√(3² -4(12)(-190)))/(2·12)

  t = (-3 ±√9129)/24

  t = (-3 ±95.546)/24 = -4.106, +3.856

The coconut will be about 10 ft off the ground after 3.856 seconds.

4.5%

step-by-step explanation: