The instructor continues in his series by discussing prime numbers and rational and irrational numbers. How many numbers are there between 1 and 20. This instructor says there are only nine numbers between 1 and 20. Watch this video and find out why.... He assumes his audience is a high school audience, but middle school and upper elementary may benefit from this video as well.[more]

Once again, the instructor is outside with a big piece of chalk and a concrete wall in a parking garage, discussing how to reduce fractions. In spite of the distraction of the background noise (sirens, garbage truck), the instruction is good.

In this video, the instructor shows how to multiply and divide fractions. After the video was made, the instructor added this: [NOTE: Correction to this problem. Youtuber LddStyx pointed out that I forgot to "kill a 7 in the breakdown of 35" so the f...inal answer to this question should be 143/12 ... Thank you, LddStyx, for the good eye.][more]

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