Selection with at Least One from a Particular Group

Selection with at Least One from a Particular Group

## Formula

If $$r$$ objects are selected from $$n$$ objects and at least one of $$m$$ specified objects must be selected:

$${}^{n}C_r-{}^{n-m}C_r$$

## Usage

- Used when a selection must contain at least one object from a specified subset.