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Building Bridges
Arithmetic Sequence
Application
Class Goals
By the end of the period, you will understand and be able to… Further examine arithmetic sequences
in the context of bridge design. Recognize and write the explicit rule for
the sequence.
Truss Bridges
Truss bridges are built using a pattern of steel beams. This pattern has great strength due to weight distribution in the beams. This activity explores the pattern of steel beams in a truss bridge design. Three beams are joined together in the triangular shape shown below.
One Section
How many steel beams form a section?
Two Sections
How many total steel beams form these two sections?
How many new beams were added to the 1st section?
Three Sections
How many total steel beams form these three sections?
How many new beams were added to the first 2 sections?
Table
Fill in the table.
Do you notice a pattern?
Total number
of bridge
sections
Additional
Beams
Total # of
Beams
1 0 3
2
3
Additional Beams
What do you notice about the number of additional beams?
Total # of Beams
Identify the pattern? Is this an arithmetic sequence or
geometric sequence? Write the recursive rule. Write the explicit rule.
One 3-D Section
How many steel beams form a section?
Two 3-D Sections
How many total steel beams form these two sections?
How many new beams were added to the 1st section?
Three 3-D Sections
How many total steel beams form these three sections?
How many new beams were added to the first 2 sections?
Table
Fill in the table.
Do you notice a pattern?
Total number
of bridge
sections
Additional
Beams
Total # of
Beams
1 0 3
2
3
Additional Beams
What do you notice about the number of additional beams?
Total # of Beams
Identify the pattern? Is this an arithmetic sequence or
geometric sequence? Write the recursive rule. Write the explicit rule.
