document.write( "Question 49930: If a pebble is dropped toward a pond from the top of a 360-ft building, its height, h, after t seconds is given by h = -16t^2 + 180. How long does it take the pebble to pass through a height of 60 feet? \n" ); document.write( "

Algebra.Com's Answer #33179 by hulamc723(15) $\"\"$ $\"About$

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If a pebble is dropped toward a pond from the top of a 360-ft building, its height, h, after t seconds is given by h = -16t^2 + 180. How long does it take the pebble to pass through a height of 60 feet?\r
\n" ); document.write( "\n" ); document.write( "well, since the height is 60, we can substitute 60 for h. we now have
\n" ); document.write( "60=-16t^2+180. Subtract 60 from both sides and you get 0=-16t^2+120 Now use the quadratic formula to solve (x= -b +or- the square root of b^2-4(a)(c)/2a)
\n" ); document.write( "In this equation a=-16, b=0, and c=120. So, now we have x=0 + or - the square root of 0-4(-16)(120)/2(-16) or x=0-(-184/32) and x=0+(-184/32) then you get x=-184/32 and x=184/32. The answer is 184/32 since time can't be negative. To simplify, divide 184 by 32 and you get 5 and 3/4 seconds. \n" ); document.write( "

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