Arrange these numbers in order from least to greatest

1/2, 0.4, 30%

So first, we need to convert all of these to the same unit. I am going to use decimals, but any one used works
So, 1/2 is the same as .5
30% is the same as .3
We already know .4
So, the order is .3,.4,.5
Simply replace the decimals with the original numbers and you get:
30%, .4, 1/2

Hope this helped!! :D