can someone please explain to me how you know where to put the 1? because sometimes my teacher puts it on the top but sometimes it’s on the bottom. i know how to move the decimal to get what i need but we are required to set it up like this and i’m so confused.

can someone please explain to me how you know where to put the 1 because sometimes my teacher puts it on the top but sometimes its on the bottom i know how to m class=