Conservation

Reduce your energy use

Students use mathematical reasoning to decide how household energy consumption might be reduced.

Activity Image
NEW
Grade
8
Duration
1 hour
Type
Group work

Overview

Using the average daily energy use of different household items, students examine the average daily energy usage rates of household appliances expressed in different forms. Students convert this data to a common form, and then make reasoned judgements about which appliances could be removed to reduce their household electricity usage the most.

Instructions

What you'll need

  • "Reflecting on my thinking" worksheet
  • "Info cards" handout (1 set per group). The cards can be separated for use. 
  • Calculators 

  1. Organize your students into small groups (3-5 students) and provide each group with a set of the "Info cards"
  2. Ask groups to select the three items that they would remove from their household to reduce their energy usage the most while still being able to live a comfortable life.
  3. Ask groups to share their decisions and thinking with the class. 
  4. Provide each student with a copy of "Reflecting on my thinking" worksheet. Ask students again to decide which three appliances they would remove from their household to reduce their energy usage the most while still being able to live a comfortable life. Prompt students to note their decisions on their worksheets. 
  5. Guide groups’ attention back to their cards. Inform groups that their task is to convert all the energy usage to a common form (e.g., rate, percent, fraction, decimals). Invite groups to share their conversions with the class. 
  6. Ask groups to order their cards from least to most energy used. Invite groups to share their card sequences with the class. 
  7. Invite groups to select the three items that they would remove from their home to reduce their energy usage the most. Encourage groups to share their decisions and thinking with the class. 
  8. Conclude the activity by asking students to return to the "Reflecting on my thinking" worksheet and their original decision. Invite them to reflect on this activity and note any changes in their thinking. 

Modify or extend this activity

Invite students to calculate their personal usage rates for various appliances.

Ask students to use the blank cards to add appliances that they use but are not included in the printed cards.

Calculate your energy bill based on the price of electricity in B.C.: 

Step 1

$0.0945 per kWh for first 1,350 in an average two month billing period (22.1918 kWh per day).

Step 2 

$0.1417 per kWh over the 1,350 Step 1 threshold.

Curriculum Fit

Mathematics 8

Content

  • Numerical proportional reasoning
    • Two-term and three-term ratios, real-life examples and problems
  • Percents less than 1 and greater than 100 (decimal and fractional percents)

Curricular competencies 

Communicating and representing
  • Use mathematical vocabulary and language to contribute to mathematical discussions
  • Explain and justify mathematical ideas and decisions
  • Communicate mathematical thinking in many ways
  • Represent mathematical ideas in concrete, pictorial, and symbolic forms
Connecting and reflecting
  • Reflect on mathematical thinking
  • Connect mathematical concepts to each other and to other areas and personal interests
  • Use mathematical arguments to support personal choices

Teaching Notes

The average B.C. energy consumption per day is 22.19 kWh, all percentages are calculated using that amount. 

The kWh/day values were converted using this website, Energy calculator.

Assessment

  • Assess students’ abilities to convert energy usage data to different forms
  • Assess students’ abilities to make decisions using mathematical data

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