Question

Matt reasoned that he can write 9/1000 as 0.9. Is he correct?

Answer 1

No he is not correct because 9/1000 Is 0.009. That is a different value than 0.9. 0.9 is 9/10.

Answer 2

The answer is no, he's not correct.

You're looking at 9/1000, which means you move the (invisible) decimal point after 9 three places to the left (because you're dividing and there are 3 zeros after the 1 in 1000). This would give you 0.009.