Permutations and Combinations

3.2 The Stocking Property

Lesson materials located below the video overview.

This grid of numbers possesses a number of curious properties. The first of them we’ll address here.


Start at any “1” on the top row, head down any number of cells, and then turn right for one cell to create a stocking. The number in the toe of the stocking always equals the sum of the numbers in the leg of the stocking.



There is a horizontal version of this stocking property also.


Exercise 32: Explain why the stocking property works. HINT: Use the fact that the number in the toe is really the sum of two other numbers in the grid.


The answer appears in the COMPANION GUIDE to this Permutations and Combinations course.


Please join the conversation on Facebook and Twitter and kindly share this page using the buttons below.

Share on FacebookTweet about this on Twitter




Take your understanding to the next level with easy to understand books by James Tanton.



Guides & Solutions

Dive deeper into key topics through detailed, easy to follow guides and solution sets.


light bulb


Consider supporting G'Day Math! with a donation, of any amount.

Your support is so much appreciated and enables the continued creation of great course content. Thanks!


Ready to Help?

Donations can be made via PayPal and major credit cards. A PayPal account is not required. Many thanks!