help needed urgently

Question

The height in metres, h, after t seconds of a bullet fired from a gun is given by . Determine the maximum height. How long before the bullet hits the ground?

Answer 1

h=100t-5t^2

0 = 100t -5t^2

t(100-5t) =0

t=0 or 20 seconds to be at ground level

another way to work this is take the derivative and set =0, the double the time

h' = 100-10t = 0

t=10 seconds is when it's at maximum height. double that to get time when it hits the ground

2(10) = 20 seconds

If this problem involves meters, the usual acceleration due to gravity is -4.9t^2. You either rounded off to-5t^2 or you're not at sea level or you're not on earth but some similar planet.