<PRE><B>Question 1021597</B>
You need to sum the geometric series
:
the sum begins at h
:
note that the ball has to bounce up and down, then
:
we need the summation from 0 to infinity of 2h(0.8)^n
:
we are give total vertical distance is 63 meters
:
if we ignore the multiplier, a geometric series will sum o to infinity to
:
1(1 - r) = 1 / (1 - 0.8) = 10 / 2 = 5
:
63 = 5(2h) - h
note we have to subtract h since we counted it and it does not count  :-)
63 = 9h
9h = 63
**********************
h = 7 meters
the ball was dropped from 7 meters
*********************</PRE>