If Our Class Were the World

10 min

Teacher Prep
Setup
5 minutes quiet think time, then whole-class discussion.

Narrative

In this activity, students apply their understanding of percentages to answer questions about the world population. It also gives them a framework for thinking about the next activity. Students have to decide how to treat a situation in which ratios are approximately equivalent. Students attend to precision as they work with large numbers and decide how to round numbers appropriately to represent whole numbers of people (MP6).

Launch

Give students 5 minutes of quiet think time followed by a whole-class discussion. Provide access to four-function calculators.

Student Task

At the time that data was collected in 2023, there were 7.9 billion people in the world. If the whole world were represented by a 30-person class:

  • 13 people would eat rice as their main food.

  • 10 people would be under the age of 20.

  • 5 people would be from Africa.

  1. What percentage of the people in the class would be under the age of 20?

  2. What percentage of the people in the class would not eat rice as their main food?

  3. Based on the number of people in the class who represent people from Africa, how many people live in Africa?

Sample Response

  1. About 33% since 10÷3010 \div 30, which is approximately 0.33.
  2. About 57%. There are 30 students, and 13 eat rice as their main food, so the other 17 do not eat rice as their main food. 17/30=0.56717/30=0.567, which is about 57%.
  3. About 1.3 billion. About 16.7% of the world's population live in Africa since 5÷30=0.1675 \div 30=0.167, and 16.7% of 7.9 billion is about 1.3 billion.
Activity Synthesis (Teacher Notes)
The purpose of this discussion is to make sure students recognize that only whole numbers are appropriate when dealing with numbers of people, which necessitates rounding and less precision in answers. Here are some questions for discussion:
  • “Would it be reasonable to say 3.2 of the 30 people in the class live in the southern hemisphere?” (No, people must be represented with whole numbers so this would be rounded to 3 people.)
  • “Does knowing that about 33% of people in the world are under the age of 20 tell us exactly how many people are in that age range?” (No, the world population and the number of people under the age of 20 are approximations, so 33% of those numbers will also be approximations rather than exact answers.)
MLR8 Discussion Supports. Revoice student ideas to demonstrate and amplify mathematical language use. For example, revoice the student statement “17 people don’t eat rice because the others do” as “17 people don’t eat rice as their main food because 13 of the 30 people do, and 30−13=1730-13=17.
Advances: Speaking
Standards
Addressing
  • 6.NS.B·Compute fluently with multi-digit numbers and find common factors and multiples.
  • 6.NS.B·Compute fluently with multi-digit numbers and find common factors and multiples.
  • 6.RP.A·Understand ratio concepts and use ratio reasoning to solve problems.
  • 6.RP.A·Understand ratio concepts and use ratio reasoning to solve problems.

10 min

30 min