Get Started With Combinatorics 3 – Parade

Alice gets tired of standing in lines and heads off to her job as a parade coordinator for the US Navy. Her boss insists that she finish planning the parade by this afternoon. "After all," he says, "there are only 7 participants in this parade. How many options are there, really?"

How many possible orderings of the 7 parade participants should Alice consider if she wants to examine them all?


The answer is 5040.

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4 solutions

Arron Kau Staff
May 7, 2014

We proceed in a similar manner to the last problem.
There are 7 options for the first participant.
There are 6 options for the second participant,
There are 5 options for the third participant,
There are 4 options for the fourth participant,
There are 3 options for the fifth participant,
There are 2 options for the sixth participant,
There are 1 options for the seventh participant,


Hence, there are 7 × 6 × 5 × 4 × 3 × 2 × 1 = 5040 7 \times 6 \times 5 \times 4 \times 3 \times 2 \times 1 = 5040 possible orders.

This can be written as 7 ! 7! which is short for 7 × 6 × 5 × 4 × 3 × 2 × 1 7\times6\times5\times4\times3\times2\times1

Alex Segesta - 7 years, 1 month ago
Brian Lee
May 9, 2014

7! (order matters) = 5040

Kevin Patel
May 9, 2014

7 ! = 7 6 ...2*1 = 5040

Asad Ullah
May 8, 2014

7!=7x6x5x4x3x2x1=5040

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