Question 185198
Each bounce results in the new height being 0.7 of the original height
HeightAtThirdZBounce=10.29m
so HeightAtSecondBound must be (10.29)/(0.7) = 14.7
and HeightAtFirstBound must be 14.7 / (0.7) = 21
finally originalHeight must be 21/(0.7) = 30m
Check your answer is {{{30*(0.7)*(0.7)*(0.7) = 10.29}}}