Final answer:
The expression 21P6 represents the number of ways to arrange 21 items taking 6 at a time and is calculated using the permutation formula: nPr = n! / (n - r)! A scientific calculator or software is recommended to evaluate this expression.
Step-by-step explanation:
The expression 21P6 refers to a permutation calculation, which is used to determine the number of ways to arrange 21 items taking 6 at a time. To calculate this on a calculator, you would generally use the permutation function or factorial function if the calculator does not have a direct permutation function. The formula for permutations is nPr = n! / (n - r)!, where n is the total number of items and r is the number of items to arrange.
To evaluate 21P6, calculate the factorial of 21 (21!) and then divide by the factorial of (21-6), which is 15 (15!). Due to the complexity of factorial calculations, it's advisable to use a scientific calculator or software that can handle such operations.