<h3>The first time when the ball will reach a height of 20 feet is 0.42 seconds</h3>
<em><u>Solution:</u></em>
Given that,
<em><u>The height of a ball thrown into the air after t seconds have elapsed is:</u></em>

<em><u>What is the first time, t, when the ball will reach a height of 20 feet?</u></em>
Substitute h = 20

<em><u>Solve by quadractic formula</u></em>




Rounding off we get,
t = 2.08 , t = 0.42
Thus the first time when the ball will reach a height of 20 feet is 0.42 seconds