The correct answer for this question is c
The answer is 9. 7 times 9 is 63 and then 63 divided by 3 is 9.
If the ball hit the ground it means that its height is equal to 0. In order to find the time after the ball <span>will hit the ground, we need to find the solution of the equation h(x)=0 which is different to 0.
-4.9x^2+21.3x=0
x(-4.9x+21.3)=0
-4.9x+21.3=0
x=21.3/4.9 = 4.3469 seconds</span>
