Based on the graph of the function that represents the rider's distance from the ground, how long will it take before the rider is at the lowest point on the Ferris wheel?

In this case we have
[tex]D(t)=10\sin (\frac{t}{20})+10[/tex]In this case we will graph the function
As we can see the lowest point is on 30 pi
[tex]D(30\pi)=10\sin (\frac{30\pi}{20})+10=10(-1)+10=-10+10=0[/tex]ANSWER
30pi seconds