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Invention Convention

Wk 3: Estimating Material Cost

Learning Outcomes: 
  • The learner will create a list of needed materials.
  • The learner will determine the cost to create the invention.
  • Fourth Grade, English Language Arts, Goal 4, Objective 1.03
  • Fourth Grade, Mathematics, Goal 1, Objective 1.04
  • Fourth Grade, Mathematics, Goal 1, Objective 1.05
  • Once all students are finished, paired students will swap “Inventor’s Logs.”  A partner will use a calculator to “assess” their partner’s work.  Should a student find a mistake, that student will explain where the mistake was made to their partner. 

In this lesson, students will compile a list of needed materials to create their inventions, and they will total the cost to build their invention using mental estimation, computation, and calculators. “Invention Convention” is an integrated project combining learning from language arts, science, and math curriculums allowing students to apply their understandings of magnets and electricity by designing or improving an existing invention.

Classroom Time Required: 

This lesson requires approximately thirty minutes. 

Materials Need: 
  • Student Inventor’s Log
  • Material Request Page (Linked in the timeline)
  • Material Cost Page (Linked in the timeline)
    • The teacher may present this as an overhead, or have students share in pairs or groups. 
  • Prior to this lesson, students should have completed “Invention Brainstorming,” “Conferencing with a Teacher,” and “Designing the Invention” lessons from the “Invention Convention” timeline. 
  • The lesson will begin whole group so the teacher can model listing necessary materials, using the cost list, recording on the material request page, estimating, computing, and finally, checking with the calculator. 
  • As a whole group, the teacher will model this activity using an invention as an example.  For an “Inside the desk light,” an inventor might need the following:  bulb, bulb holder, wire, battery, battery holder, glue, and bulb shade.  The teacher will model using the design sketch made in a previous lesson to ensure that all materials are listed.  Once the materials are listed, the teacher will model recording the prices, found on the Material Cost page.  The teacher will then model using mental estimation to estimate the cost.  Next, the teacher will compute the price using pencil and paper.  Last, the teacher will use the calculator to check the computation work.  Finally, the teacher will model duplicating the list of materials on the extra “Material Request Page.”  (Students may wonder why they have to copy the list.  The reason is the student, i.e. inventor, must retain a copy in their Inventor’s Log, but the teacher will need a copy to ensure that each student has all the supplies necessary to build the invention. 
  • Once the students understand the expectations, the students will work independently. 
  • Because the whole group lesson involved a visual component, ELLs should be able to complete this activity independently.
  • ELLs may need some assistance identifying different materials on the Materials Cost page.  (An illustrated Materials Cost Page would be helpful, or assign ELLs a partner to help identify materials.)
  • This lesson offers an opportunity for teaching pluralization.  For novice learners, the teacher may choose to introduce adding “s” or “es” to words representing more than one thing.  For intermediate learners, a teacher may introduce pluralizing words ending in “y.”  For advanced learners, teachers may introduce the difference between the words:  this, that, these, those.  These language learning objectives can be incorporated onto the Materials Request page. 
Author's Comments: 
  • Although families donate the majority of materials, it is helpful for students to consider that when designing an invention, there are costs for each part needed. Also, parents are very appreciative of the time and effort teachers provide ensuring that each student has supplies necessary, and this appreciation is sometimes formed when noticing the cost of their child producing an invention. 
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