Explanation:
B = 1 4/5
because 1 is completely to the left, and from the distance between 1 and 2 B is at the end of the 4th of 5 sub-segments.
and 1 4/5 would be also 9/5, because B includes the 5 sub-segments (of 5) between 0 and 1. and then the 4 of 5 sub-segments between 1 and 2. so that are 9 sub-segments in total.
and each sub-segment represents 1 out of 5 (= 1/5) parts of each number interval.
therefore, we have 9×1/5 = 9/5.