Question: Imagine a disk spinning like a record player turn table. Half of the disk is black and the other is white. Assume you have an unlimited number of color sensors. How many sensors would you have to place around the disk to determine the direction the disk is spinning? Where would they be placed?
Options:
(A) 1
(B) 2
(C) 3
(D) 4
(E) 5 Let's think first. Some random reasoning:
1 sensor between the black and white border on the edge of disk
1 is enough to determine the drection The final answer: (A).