Find the rule, fill in 1 / 2, 0.2, 2.5, 0.4, 4 1 / 2, 3 / 5, (), 80% 1 / 2 (this is half), 0.2, 2.5, 0.4, 4 1 / 2 (this is four and half), 3 / 5 (three fifths), (), 80% Please explain why

Find the rule, fill in 1 / 2, 0.2, 2.5, 0.4, 4 1 / 2, 3 / 5, (), 80% 1 / 2 (this is half), 0.2, 2.5, 0.4, 4 1 / 2 (this is four and half), 3 / 5 (three fifths), (), 80% Please explain why

1/2、0.2、2.5、0.4、4 1/2、3/5,(13/2),80%
Item 1 / 2
The third 2.5 = 5 / 2
Item 5 4 1 / 2 = 9 / 2
So the seventh is 13 / 2
2、 Four, six and eight were 0.2, 0.4, 0.6 and 0.8, which increased by 0.2 in turn