Main Idea and Key Details is a free printable Grade 3 English worksheet on matching a main idea to the key detail that supports it, aligned to Common Core standard RI.3.2. It prints 3 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 21 of 25 · the same problems every time you open this link.
Set 1 has all 25 in a single PDF. All 25 sets ask different questions.
Main Idea and Key Details
RI.3.2
NameDate
Write the letter of the detail next to each main idea.
1.Write the letter of the key detail that supports each main idea.
Beavers change rivers by building dams.
A canal lock lets boats climb hills.
Volcanoes form where melted rock escapes from the Earth.
Swallows leave Britain to follow their food.
A.Lava pours out through a crack and cools into rock.
B.Water flows in and the boat rises with it.
C.Flying insects disappear in October.
D.They pile up sticks and mud until the water backs up.
2.Write the letter of the key detail that supports each main idea.
Trees help keep soil in place.
Morse code turns letters into short and long signals.
A windmill turns moving air into turning stone.
Yeast makes bread rise.
A.It gives off gas that is trapped in the dough.
B.E is one dot and T is one dash.
C.Their roots hold the earth together in heavy rain.
D.The sails turn a shaft that turns the millstone.
3.Write the letter of the key detail that supports each main idea.
A salmon returns to the river where it hatched.
Frogs change shape as they grow.
Cheese is made by separating the protein in milk.
Lighthouses keep ships away from rocks.
A.Their lamps flash a pattern sailors can see at night.
B.Rennet splits the milk into curds and whey.
C.A tadpole grows back legs before front legs.
D.It finds the river by its smell.
LessonPrint · RI.3.2 · Set 21 · free to copy for classroom use
Answer key — Main Idea and Key Details
Set 21. Prints on its own sheet.
1.1. Beavers change rivers by building dams. — D (They pile up sticks and mud until the water backs up.) 2. A canal lock lets boats climb hills. — B (Water flows in and the boat rises with it.) 3. Volcanoes form where melted rock escapes from the Earth. — A (Lava pours out through a crack and cools into rock.) 4. Swallows leave Britain to follow their food. — C (Flying insects disappear in October.)
2.1. Trees help keep soil in place. — C (Their roots hold the earth together in heavy rain.) 2. Morse code turns letters into short and long signals. — B (E is one dot and T is one dash.) 3. A windmill turns moving air into turning stone. — D (The sails turn a shaft that turns the millstone.) 4. Yeast makes bread rise. — A (It gives off gas that is trapped in the dough.)
3.1. A salmon returns to the river where it hatched. — D (It finds the river by its smell.) 2. Frogs change shape as they grow. — C (A tadpole grows back legs before front legs.) 3. Cheese is made by separating the protein in milk. — B (Rennet splits the milk into curds and whey.) 4. Lighthouses keep ships away from rocks. — A (Their lamps flash a pattern sailors can see at night.)
More practice for RI.3.2
State the main idea and show which details hold it up.