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Unit III Lesson 4

Permutations and Combinations and Factorials

A factorial ( ! ) is a math symbol for a special kind of multiplication; check it out. You will need it for some of these problems.

Probability (lesson 3) asks "what are the chances?"  In permutations and combinations, you ask "how many ways?"  In combination problems, order is not important; with permutation, order is important.

Starting with permutations, I agree with Sal at Khan that it is better to understand permutations rather than just learn to apply the permutation formula, so start here with permutations, learn about factorials, and go through the subsequent videos one by one till you get to test yourself at the end. If you go through all the Khan videos in order, you will not have any trouble doing the practice problems. 

Next, start here for the videos on combinations, and then try out some combination problems.  And the BIG TEST:  try out these problems with a mix of combination and permutation problems!

You can review the definitions and illustrations of combinations and permutations at MathisFun, and test your understanding with the interactive questions "your turn" at the end of that page.

You can also go to the regents prep site to practice more of these kinds of problems.

END OF UNIT III - Onward to topics under Algebraic Reasoning (Units IV, V, VI, VII)