Ratios, Ratios ... Everywhere
It has been argued that proportional reasoning is one of those important building blocks in Middle School. This page includes activities to help connect Middle and High School topics that draw on students' proportional understanding.
Why we can cross-multiply
Cross-multiplying is also one of those procedures that students do incorrectly too often. This first activity aims to get at that understanding through context and multiple ways of representing ratios.
Many students see a larger triangle of the same shape (a similar triangle) as having "bigger" angles. This may be because they have not mastered the use of a protractor to measure angles. Before proceeding to this activity, it may be important to check to see if students can measure angles.