Briefly discuss how Excel modifies cell references when copying and pasting formulas, including an explanation of absolute, relative, and mixed cell references.

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Excel modifies cell references when copying formulas. While copying formulas, however, sometimes you do not want Excel to change cell references. To keep a cell reference constant when copying a formula or function, Excel uses a technique called absolute cell referencing. To specify an absolute cell reference in a formula, enter a dollar sign ($) before any column letters or row numbers you want to keep constant in formulas you plan to copy. For example, $B$4 is an absolute cell reference, whereas B4 is a relative cell reference. Both reference the same cell. The difference becomes apparent when they are copied to a destination area.

A formula using the absolute cell reference $B$4 instructs Excel to keep the cell reference B4 constant (absolute) in the formula as it copies it to the destination area. A formula using the relative cell reference B4 instructs Excel to adjust the cell reference as it copies it to the destination area. A cell reference with only one dollar sign before either the column or the row is called a mixed cell reference. When planning formulas, be aware of when you need to use absolute, relative, and mixed cell references.