You do not. If you reduce 64:60, you will get 16:15 which is not the same as 16:4
Assuming Earth's gravity, the formula for the flight of the particle is:
s(t) = -16t^2 + vt + s = -16t^2 + 144t + 160.
This has a maximum when t = -b/(2a) = -144/[2(-16)] = -144/(-32) = 9/2.
Therefore, the maximum height is s(9/2) = -16(9/2)^2 + 144(9/2) + 160 = 484 feet.
I think it should equal 70 but not 100%
