This is kinda hard to explain but I'll try my best. Here's a tip, the fractions that are on the ruler really mean 10,20,30,40,50,60,70,80,90, and 100. So, when you look at the decimals on number 7, you have to try to turn them into fractions in your head. For example, 0.9 is actually 9/10 or 90.
It's easier to go ahead an find out the decimals that the fractions turn into. To find the decimals just divide the numerator by the denominator so 1/10 is 0.1 and 2/10 is 0.2 and so on. Then placing the decimals on the ruler from there is simple. like 0.09 will be before 1/10, 0.19 will be before 2/10
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