How to automatically calculate column cell value?

Question

Google Sheets

The simplest case. There is a table. Data is entered into column B through forms.
In the adjacent column in cell C I want to see the percentage of the corresponding cell in column B .
I know how to enter this value for already existing cells. But I don’t know how to make it automatically considered for new values.
Those. Let's say I entered a new value through the form. It was displayed in B5, I need the value calculated from B5 to appear in cell C5.

Answer 1

creating the required formula in cell C1 and dragging it down doesn't it help?

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