Ferris wheel trig question

Question

A Ferris wheel is 40 meters in diameter and boarded from a platform that is 1 meters above the ground. The six o'clock position on the Ferris wheel is level with the loading platform. The wheel completes 1 full revolution in 6 minutes. How many minutes of the ride are spent higher than 31 meters above the ground?



Answer 1

31 < 20 sin (2πt / 6) + 1

Solve for firs two values of t.

Subtract smaller form larger and answer