CCSS: 6.RP.3, MP#2 – Reason Abstractly and Quantitatively

Instructional Format: Video, student problem-solving, group or individual work

Lesson Description: There are many ways to use this video in your math class. I filmed it with the express purpose of having students practice using reasoning skills with problems involving measurement and ratios. There are A LOT of decisions and assumptions that students will need to make when trying to solve this problem. Because the shape of the bridge isn’t a basic square or rectangle and more of a squished semi-circle (times 2), they are going to have to make some big leaps on figuring out how many meters of steel are on the bridge before they work on the ratio.

1) You can show this video (1:39) at the beginning of any unit You can have them work on the problem at the end of daily lessons (or once a week) armed with new knowledge that they are exploring in class. Students use the note-maker to help record their problem-solving work. Or you could revisit the video at the end of any unit as a formative check to see what the students have learned about working with ratios and/or measurement and whether they can apply that knowledge.

2) You could show this video as a warm-up activity after the students have learned some ratio reasoning. It is a great way to explore the real-life application of measurement and ratios.

Extension: The extension to this problem is based on engineering research. Rivets aren’t screwed into place, but I didn’t want the video to go off on a bird walk, so I said that for speed. When touring the bridge, it was very apparent that safety wasn’t much of a concern in construction in the early 1900’s. It could be a great research project for an interested student to explore.

Cautionary notes/ misconceptions/additional connections: Students may want to think about the x-shaped structures between the two outside steel curves on the bridge and how much length that may add to the final amount of total steel number. It might be fun for students to make smaller drawings and try to determine if they can approximate the additional amount of steel.

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