Date of the Problem
February 21, 2023


Civil engineers design and build all sorts of infrastructure projects, such as bridges, buildings, roads and railways. Civil engineers must be precise and technical, creative and flexible to ensure the infrastructure people use every day is efficient and safe. 

A common type of bridge is called a truss bridge, which uses equilateral and/or isosceles triangles to strengthen its structure. Triangles can take weight from a single point and distribute it across a wide base, so it is a common shape used in constructing buildings and bridges. There are many different types of truss bridges with different designs and layouts of the triangles, one of which is called the Pennsylvania truss (shown here).



2.1  How many triangles of any size are there in the Pennsylvania truss bridge shown? 

2.2  The triangles in the circled section of the bridge are all similar right isosceles triangles. Using the measurements provided here (in feet), how many feet of steel will be needed to construct this section alone? Express your answer as a decimal to the nearest tenth. 



2.3  Refer to the previous enlargement of the circled section of the bridge. In this section of the bridge, the area of the smallest triangle is what fraction of the area of the largest triangle? Express your answer as a common fraction.




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CCSS (Common Core State Standard)