We could solve this by using the Fundamental Counting Principle, but that would be cumbersome because we would have to multiply 15 numbers. A much easier way to solve the problem is to recognize that, by definition, the number of ways to arrange 15 people is 15! According to the calculator,
This number is in scientific notation. Do you remember how to write it as a standard numeral? (We move the decimal point 12 places to the right.)
= 1,300,000,000,000 (about 1.3 trillion).