Question

During a practice match, a softball pitcher throws a ball whose height can be modeled by the equation h = $-25t^2$ + 40t - 12, where h = height in feet and t = time in seconds. How long does it take for the ball to reach a height of 4 feet?

• A. 2.2, 3.8 secs
• B. 0.4, 0.2 secs
• C. 0.8, 0.8 secs
• D. 7.5, 0.5 secs

Answer 1

The correct option is C

0.8, 0.8 secs

Given, height = 4 = -25$t^2$ + 40t - 12

$\Rightarrow$ 25$t^2$ - 40t + 16 = 0

$\Rightarrow$ (5t - 4) (5t - 4) = 0

t = $\frac{4}{5}$,$\frac{4}{5}$ or 0.8, 0.8

It takes 0.8 secs and 0.8 secs for the ball to go up and down respectively.