Which county generated more solar power – the United States or China?

Grade level:  3rd- 5th grades

Skills: Circle graph

Related environmental issues: Energy

The circle graph below shows five countries that generated the largest amount of solar power, electricity generated from solar energy, in the world in 2017.


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  1. What country generated the largest amount of solar power in the world?
  2. What percentage did the United States make up?
  3. What country generated twice as much solar power as Italy?
  4. Did China make up more or less than the rest of the world combined?

Sources: REN 21, 2018



Answer keys

  1. China
  2. 13%
  3. Germany
  4. more

How much has the weight of plastic bottles changed?

Grade level: 3rd – 5th grades

Skills: Division 

Related environmental issues: Reduce /  Reuse / Recycle

The average weight of  plastic beverage bottles has changed over time. In 1980, five empty 2-liter PET bottles weighed 340 grams.  Now, nine 3-liter PET bottles weigh 378 grams.


  1. Which weighs more, a plastic bottle in 1980 or now? And how much?
  2. Why do you think has the weight of plastic bottles changed? Explain.

Sources: PET Resin Association, Little-Known Facts about PET Plastic




Answer keys

  1. 1980 bottle: 340 ÷ 5 = 68 (g)   Now: 378 ÷ 9 = 42 (g)    68 – 42 = 22 (g)     A plastic bottle now is 22 g lighter than that in 1980.
  2. Answers may vary: Hint 1) Lightweight plastic bottles reduce the use of plastic and raw materials  2) Lightweight plastic bottles reduce overall weight of the item and reduce energy consumed and CO2 emitted in the process of manufacturing and transporting the item. 3) Lightweight plastic bottles reduce plastic (and raw materials) use, so does the amount of plastic that has to be recycled.