Hello, Richard,
If you graph the equation y=-16x^2+149x+108 a couple of things pop out. First, y = 108 at time = 0. The rocket is fired from a starting point 108 feet. Perhaps from a hill, or from a platform. But the problem states tower, which I had initially disregarded. This is important since when it states " . . . to reach ground, one needs to make an assumption of at level ground is. For this problem, I'll define ground as 0 feet, by custom the reference point.
The second observation from the graph is that it crosses the x axis at around 10 seconds. That must be close to the answer, but the question asks for the nearest 100ths of a second. There are two things to be learned from the total flight time and requested precision. This must be another failed NASA launch to have been in the air only 10 seconds. The rubber band must have snapped.
Since high precision is required, we should solve the actual equation. Do this by setting y to 0 (ground level) and solve for t. It's a quadratic equation, so use the Quadric formula. I found an answer of 9.99 seconds.
Bob
