A waterfall has a height of 1500 feet. A pebble is thrown upward from the top of the falls with an initial velocity of 20 feet per second. The height, h, of the pebble after t seconds is given by the equation h=-16t^2 + 20t + 1500. How long after the pebble is thrown will it hit the ground?

The pebble will hit the ground about [___] seconds after it is thrown.

(Simplify your answer. Round to one decimal place as needed.)