Need to find the greatest common factor for a set of numbers? Easy as cake. Learn how to find GCFs using the upside-down birthday cake method with this free video lesson. From Ramanujan to calculus co-creator Gottfried Leibniz, many of the world's best and brightest mathematical minds have belonged to autodidacts. And, thanks to the Internet, it's easier than ever to follow in their footsteps (or just finish your homework or study for that next big test).

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