How are we protected from dangerous air pollution?

Grade level: 4th – 6th grades

Skills: Place value (whole numbers)

Related environmental issues: Air

Clean air is essential for our health.The United States has protected Americans from dangerous air pollution that cause asthma, lung diseases, and early death by enacting the law called the Clean Air Act. It is estimated that the Clean Air Act will save at least 230,000lives by 2020 in this country.


  1. What digit is in the tens place of 230,000?
  2. What place is the 3 in 230,000?
  3. How many thousands are in this number?
  4. How many hundreds are represented by the 2?
  5. How many ones are represented by the 3?
  6. Which number represents 230,000?
a.23  x 102
b.23 x 103
c.23 x 104
d.23 x 105


Source: U.S. EPA, Clean Air Act Overview.

Photo: WWF


Answer keys

2.Ten thousands




The 225 Math Quizzes That Will Make You An Environmental Expert (2019) is available from  (paperback)

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How many species are threatened with extinction?

Grade level: 5th grades

Skills: Place Value 

Related environmental issues: Biodiversity

At the present time, there are 28,338 kinds of plants and animals (species) that are at risk of becoming scarce within the foreseeable future in the world. They are threatened with extinction mainly because they lost their homes. Humans are responsible for the habitat loss when they destroy their habitats by developing housing, highways, industry, and agriculture.


1. what is the value of the underlined digit in 28,338?

2. What digit is in the tens place in 28,338?

3. What place is the 2 in 28,338?

4. What is the relationship between the values of the underlined digits?

  • 28,338 and 28,338
  • 28,338 and 28,338

Sources: IUCN Red List of Threatened Species (Table 1-b), 2019


Answer keys

1. 8,000

2. 3

3. ten thousands

4. When comparing the underlined digits, the first 8 represents 8 thousands, whereas the latter 8 represents 8 ones

When comparing the underlined digits, the first 3 represents 3 hundreds, whereas the latter 3 represents 3 tens