What are Ratios and Proportions?

What are ratios and proportions? In today's math lesson we go over the definitions of both, and how they are related. A ratio simply relates two quantities, for example, 50 miles per hour is a relation of 50 miles to 1 hour. A recipe might call for 3 eggs for every 10 pancakes, in which case you have a ratio of 3 eggs to 10 pancakes. A proportion relates a ratio to a ratio, and in particular, says they are equal. For two ratios to be proportional, they must be equal. For example, the ratio 2 : 5 is proportional to the ratio 4 : 10. They are equal, which becomes crystal clear when you reduce them as fractions. 2/5 cannot be reduced, and 4/10 reduces to 2/5, thus they are equal. When triangles are proportional, it means that the ratios of their corresponding sides are equal. For example, if we have a triangle with side lengths 1, 2, and 3 units, and a triangle with side lengths 2, 4, and 6 units, then they are similar triangles because the ratios of their corresponding sides are proportional (1/2 = 2/4 = 3/6). Let me know if you want more lessons on similar triangles.

I hope you find this video helpful, and be sure to ask any questions down in the comments!

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