What exactly is the rule of this? (in words)

7.5 x 1000 = 7500
5.9 x 10 = 59
9.4 x 100 = 940

8.3 / 1000 = 0.0083
6.5 / 10 = 0.65
6.6 / 100 = 0.066

/ means divided by
x means multiply