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Main Idea and Its Support is a free printable Grade 4 English worksheet on working out a main idea from the details that support it, aligned to Common Core standard RI.4.2. It prints 8 questions with an answer key on its own sheet of paper, in 25 versions that each ask different questions, so no two students in the class work from the same page. Print it from the browser or download it as a PDF — no account, no email.

Set 20 of 25 · the same problems every time you open this link.

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Set 1 has all 25 in a single PDF. All 25 sets ask different questions.

Main Idea and Its Support

RI.4.2

NameDate

Circle the right answer.

1.A paragraph says: Fleming saw mold kill germs; Florey and Chain found a way to make it in large amounts; by 1944 it was treating soldiers. What is its main idea?
  • A.Soldiers were wounded in 1944.
  • B.Mold grows in dishes.
  • C.Making penicillin into a medicine took the work of many people.
2.A paragraph says: some volcanoes pour out rivers of lava; others explode in clouds of ash; some have been quiet for thousands of years. What is its main idea?
  • A.Lava is hot.
  • B.Volcanoes behave in different ways.
  • C.Ash is gray.
3.A paragraph says: beavers fell trees with their teeth; they build dams of sticks and mud; their ponds give homes to fish and birds. What is its main idea?
  • A.Beavers change the places where they live.
  • B.Fish live in ponds.
  • C.Beavers have sharp teeth.
4.A paragraph says: earthworms tunnel through soil and let air in; they drag dead leaves underground; their waste makes the soil richer. What is its main idea?
  • A.Leaves fall in the fall.
  • B.Earthworms help keep soil healthy.
  • C.Earthworms live underground.
5.A paragraph says: early phones were fixed to the wall; later phones had no cord; today's phones fit in a pocket and take photos. What is its main idea?
  • A.Walls hold phones.
  • B.Phones take photos.
  • C.Telephones have changed a great deal over time.
6.A paragraph says: trains ran to schedules across the country; each town had kept its own time; the railways needed one time everywhere. What is its main idea?
  • A.Towns had clocks.
  • B.Trains were often late.
  • C.The railways led to one time for the whole country.
7.A paragraph says: Arctic foxes grow a thick white coat in winter; their small ears lose little heat; fur on their paws stops them slipping. What is its main idea?
  • A.Arctic foxes are white.
  • B.Ice is slippery.
  • C.Arctic foxes are suited to the cold.
8.A paragraph says: coral reefs cover a tiny part of the sea floor; a quarter of all sea creatures live on them; many fish lay their eggs there. What is its main idea?
  • A.Fish lay eggs.
  • B.Coral reefs are very small.
  • C.Coral reefs are home to a great deal of sea life.

LessonPrint · RI.4.2 · Set 20 · free to copy for classroom use

Answer key — Main Idea and Its Support

Set 20. Prints on its own sheet.

  1. 1.Making penicillin into a medicine took the work of many people.
  2. 2.Volcanoes behave in different ways.
  3. 3.Beavers change the places where they live.
  4. 4.Earthworms help keep soil healthy.
  5. 5.Telephones have changed a great deal over time.
  6. 6.The railways led to one time for the whole country.
  7. 7.Arctic foxes are suited to the cold.
  8. 8.Coral reefs are home to a great deal of sea life.

More practice for RI.4.2

State the main idea, show the details behind it, and summarize.

Teaching this next? The Main Idea and a Summary is the 40-minute plan for it, with the misconceptions to expect.

All Grade 4 worksheets

Last reviewed 2026-09-05. Aligned to RI.4.2 of the Common Core State Standards for English Language Arts.