Free proportion videos online (pre-algebra/grade 7)

Find here free online math videos on proportions-related topics: solving proportions, unit rate, proportional relationships, and scaling geometric figures. These videos are suitable for pre-algebra / grade 7, and are aligned to the Common Core standards concerning proportions in grade 7 math. The videos are recorded in high-density (HD) and are viewable both here as well as at my Youtube channel.

72 pages (includes answers) PDF download $4.00 Printed copy $11.80, b&w

Math Mammoth Ratios, Proportions & Problem Solving Sample pages (PDF) Contents and Introduction Solving Problems Using Equivalent Ratios Scaling Figures 2 Problem Solving with Diagrams, part 1 Ratio Problems & Bar Models 2 Buy download at Kagi (credit cards, Paypal, check, cash, PO, wire transfer, money order; see Kagi shopper help) Buy printed book at Lulu (credit cards, Paypal, PO) Este libro en español

Solving proportions

Proportion is defined as an equation of the type (ratio) = (ratio). I show three different ways of solving proportions:
1) table
2) thinking of equivalent fractions
3) cross-multiplying

Then I solve several word problems that involve proportions using these methods.

Unit rates and more about proportions

A unit rate is a rate where the second term in the rate is 1 of something, such as $5 per $1 or 65 miles : 1 hour. You can always solve the unit rate from a non-unit rate by dividing. For example, if you have the rate $46 per 6.5 hours, divide $46 by 6.5 to get the rate per 1 hour.

I solve word problems involving unit rates, and also show how unit rate relates to SLOPE in a linear equation. Basically, slope gives you the unit rate!

Proportional relationships / Direct variation

How can we determine if two variables are in a proportional relationship or not? If you write a table of the values of the two variables, when one variable increases by some certain amount, the other should also increase by some certain amount. Another way to know is if you graph the equation that involves the two variables. You should get a straight line through origin, and if that is the case, the slope gives you the unit rate. (Or, just look at the equation that relates the two variables: it should be of the form y = kx.)

I also show an example of a non-proportional relationship, which ends up being an inverse variation. Proportional relationships are also called direct variation.

Scaling figures and the scale ratio

When a figure is enlarged or shrank proportionally, or when two figures are similar, the scale ratio is the ratio of one side of the figure to the corresponding side in the other. When the scale ratio is given, we can solve an unknown side. Or, if a set of corresponding sides is given, we can write a proportion to solve for the unknown side.

This lesson is meant for prealgebra or grade 7 math.

The videos match the lessons in my book Math Mammoth Ratios, Proportions, and Problem Solving (Blue Series book), or the lessons in chapter 2 of Grade 6-A. In any of those books, you will get MANY more practice exercises, word problems, and puzzles than what are shown in the videos, and also some lessons that are not in covered in this set of videos.

72 pages (includes answers) PDF download $4.00 Printed copy $11.80, b&w

Math Mammoth Ratios, Proportions & Problem Solving Sample pages (PDF) Contents and Introduction Solving Problems Using Equivalent Ratios Scaling Figures 2 Problem Solving with Diagrams, part 1 Ratio Problems & Bar Models 2 Buy download at Kagi (credit cards, Paypal, check, cash, PO, wire transfer, money order; see Kagi shopper help) Buy printed book at Lulu (credit cards, Paypal, PO) Este libro en español