Stars and Bars - Mastering AMC 10/12

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In this video, we will cover Stars and Bars, one of the most powerful shortcuts to combinatorics problems on the AMC 10/12.

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For more practice, watch the AMC 10/12 Fundamentals Classes here:

If you need a refresher on the fundamentals, check out:
1. AMC 8 Fundamentals:

2. AMC 8 Advanced:

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Tags:
AMC 10, AMC10, AMC 12, AMC12, AMC 10 Preparation, AMC 10 Crash Course, AMC 10 Concepts, AMC 12 Preparation, AMC 12 Crash Course, AMC 12 Concepts, AMC 10 Review, AMC 12 Review, Number Theory, Primes, Factors Competition math, number of factors, sum of factors, product of factors, AMC 10 number theory, AMC 12 number theory, diophantine equations, divisibility competition math, Area of a Triangle, Similar Triangles, Cyclic Quadrilateral, Power of a point, 3D Geo, Polygons, Coordinate Geometry, Trigonometry, Logarithms, Complex Numbers, Inequalities, Floor and Ceiling Functions, Generating Functions

[pranavsirur]

Why is it not: if you have N things and you want to pick K with potential repetition, you have (N + K - 1) choose K options

[mayflowerimpact]

Great video! What app do you use to show all the work? Also, can you share the link to the digital pen you use? Thank you!

[haha-untk]

what do you mean when you refer to the 2 bars and 7 acorns as 9 spots? how would the bars count as spots for the acorns to go in? 11:40

[huihuixiao]

Why do you need four bars for the first question? Is it necessary to have the 1?

[davidma]

Why choose from n-4 +4? Shouldn't it be n-4+4-1?