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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 10 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: 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.Volcanoes behave in different ways.
  • B.Lava is hot.
  • C.Ash is gray.
2.A paragraph says: plastic bags take hundreds of years to break down; turtles mistake them for jellyfish; many towns now charge for bags. What is its main idea?
  • A.Turtles eat jellyfish.
  • B.Stores sell bags.
  • C.Plastic bags harm the natural world.
3.A paragraph says: libraries lend books for free; many offer computers anyone can use; they run reading clubs for children. What is its main idea?
  • A.Computers are useful.
  • B.Libraries offer many free services to a town.
  • C.Children like clubs.
4.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.Beavers have sharp teeth.
  • C.Fish live in ponds.
5.A paragraph says: Roman roads ran straight for miles; they were laid in layers so water drained away; some are still used today. What is its main idea?
  • A.Romans liked straight lines.
  • B.Roman roads were built to last.
  • C.Water drains away.
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.The railways led to one time for the whole country.
  • B.Trains were often late.
  • C.Towns had clocks.
7.A paragraph says: lighthouses warn ships away from rocks; each one flashes its own pattern; sailors use the pattern to tell where they are. What is its main idea?
  • A.Rocks are dangerous.
  • B.Lights can flash.
  • C.Lighthouses keep ships safe and help them find their way.
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.Coral reefs are home to a great deal of sea life.
  • B.Fish lay eggs.
  • C.Coral reefs are very small.

LessonPrint · RI.4.2 · Set 10 · free to copy for classroom use

Answer key — Main Idea and Its Support

Set 10. Prints on its own sheet.

  1. 1.Volcanoes behave in different ways.
  2. 2.Plastic bags harm the natural world.
  3. 3.Libraries offer many free services to a town.
  4. 4.Beavers change the places where they live.
  5. 5.Roman roads were built to last.
  6. 6.The railways led to one time for the whole country.
  7. 7.Lighthouses keep ships safe and help them find their way.
  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.