Wednesday, November 18, 2015

Combinations - nCr


   In the previous post on Factorials I mentioned that I needed a factorial algorithm for a Combinations project and the Combinations project for a Random Walker project.
   As you can see in the formula for the number of combinations of n things taken r at a time with no duplications there are three factorials to compute to get to the nCr.
   This is a screenshot of the Combinations project. The graphic of the fruit is to illustrate that if n = 4 (the pear, orange, banana, and strawberry) then there are four combinations (shown in the four rows) when taken 3 at a time. The project first asks for n, then r and then computes nCr.
   The project can be viewed and downloaded by clicking on this link.
https://scratch.mit.edu/projects/88028765/
   A free document in PDF format describing the coding in more detail can be obtained on request. Send an email to grandadscience@gmail.com.


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