How to keep one variable constant with other one changing with row in excel

Question

Let's imagine I wish to maintain a constant value in cell A1 for the purposes of a calculation. For instance, I wish to determine the following value:

=(B1+4)/(A1)

How can I get A1 to constantly refer to that cell rather than going to A2, A3, etc. when I drag that cell to perform a calculation over cells in several rows?

Answer 1

Use this form:

=(B0+4)/$A$0

Since you are dragging across rows, you really only need to freeze the row part:

=(B0+4)/A$0