A projectile is launched upward from the ground at an initial velocity of 400 feet per second. During it’s upward flight, the projectile passes a hot air balloon floating at a constant height of 2400 feet. How many seconds later will the projectile pass the hot air balloon again on the way down?

Answer 1

you want to solve for t in

400t - 16t^2 = 2400

Then find the difference in the two times.