Final answer:
The riders will be more than 15 m above the ground when the given water tube ride function is greater than 15.
Step-by-step explanation:
The given model of the water tube ride can be represented by the function h(t) = -0.002t4 + 0.104t3 - 1.69t2 + 8.5t + 9, where t is the time in seconds and h is the height in meters above the ground.
To find when the riders will be more than 15 m above the ground, we need to solve the inequality h(t) > 15.
By substituting the function into the inequality, we get -0.002t4 + 0.104t3 - 1.69t2 + 8.5t + 9 > 15.
This inequality can be solved either graphically or numerically to find the time t when the riders will be more than 15 m above the ground.