Main Idea and Supporting Details

Main Idea and Supporting

In this lesson, you’ll discover
that an author communicates one big idea and gives details about it.
THE MAIN IDEA is what a
selection’s mostly about—the most important thing the author wants readers to
know. Other facts in the selection are details that support, or tell more
about, the main idea. Sometimes the main idea is stated directly.

Example 1
Grass is one of Earth’s most
useful plants. Most people think of it as the stuff that grows in the yard and
needs to be mowed, but there are thousands of different kinds. Wheat, rice, and
other grains are grasses that help people and animals exist!
The main idea is stated: Grass
is a useful plant. But sometimes you have to find the main idea yourself. To do
that, use information from the text to figure it out.

Example 2

In 1483, Italian artist
Leonardo da Vinci sketched a flying machine. He was also a scientist and
fascinated by movement. His sketch showed a screw-like wing made of stiff
linen. He never got it off the ground, but a real helicopter like it flew
almost 500 years later!
The main idea is that Leonardo
da Vinci designed the first helicopter more than 500 years ago. That’s what the
author most wants you to remember.
In the first example,
supporting details are that wheat, rice, and other grains are useful grasses,
and people and animals need grasses. In the second example, details are the
year he drew the design, that it was a flying machine, what it looked like, and
when the first real helicopter flew. Each detail supports or expands on the
main idea.
In longer selections, each
chapter or section may have its own main idea, but there’s just one central
idea for the whole selection. Sometimes the title can help you figure out the
main idea. And you may find that some details add interest but aren’t necessary
to finding the main idea, like the fact that da Vinci was fascinated by
movement, so they are not “supporting” details.

Main Idea and Supporting
Details Practice Exercises

Practice 1: A Musical Mouse
Read the selection, and then
answer the questions that follow.
(1)     There are many different kinds of mice. Some are good swimmers;
others like to swing from trees by their tails. And one kind, the white-footed
mouse, is not only a good swimmer and tree climber, but it’s also quite
(2)     This minute, furry creature’s body is about 8 inches (20 cm)
long, with a tail of another 3 inches (7.5 cm). It weighs only about 0.8 ounces
(23 g). It’s been around North America for a long time; scientists have found
40- million-year-old fossils of the tiny creature’s ancestors!
(3)     Some people call the white-footed mouse the “wood
mouse” because it lives in so many wooded areas throughout North America.
Other people call the white-footed mouse the “deer mouse.” One reason
is that its fur is the same colors as a deer’s—soft brown on its back; white on
its underside. Another reason is that the mice carry deer ticks that spread
Lyme disease.
(4)     The whitefoot makes its nest almost anywhere. It likes a home
that is warm and dry, like a hollow tree or empty bird’s nest. But most of the
time the whitefoot runs along the ground looking for food. It eats seeds, nuts,
leaves, bark, and insects. It sleeps by day and looks for food at night—its
long whiskers and big ears help it find its way in the dark.
(5)     Does the whitefoot really make music? In a way, it does because
it often makes a humming sound. And it taps its little paws very fast on a dead
leaf or hollow log to make a buzzing, drumming sound! Scientists aren’t sure
why the mouse is a drummer; it just is!
(6)     So the next time you’re in the woods, walk quietly. There might
be a white-footed mouse nearby, and you wouldn’t want to interrupt a mouse in
the middle of its song . . . would you?
1.       What is the main idea of this selection?
          a.       Deer are
brown and white.
          b.       The
white-footed mouse taps its paws in a drumming sound.
          c.       The woods of
North America are full of mice.
          d.       Scientists
study the habits of mice.
2.       Which is a supporting detail for that main idea?
          a.       The
white-footed mouse is also known as the wood mouse.
          b.       The deer
mouse may carry ticks that transmit a disease.
          c.       The mouse
taps on a dead leaf or hollow log.
          d.       The
white-footed mouse isn’t very big.
3.       Which would make the best substitute title for this selection?
          a.       “How to
Build a Better Mousetrap”
          b.       “Concert
in the Woods”
          c.       “Caution:
Lyme Disease Ahead!”
          d.       “All
about Rodents”
4.       What is the main idea of paragraph 2?
          a.       The
white-footed mouse lives in Canada.
          b.       The
white-footed mouse is also called the wood or deer mouse.
          c.       The
white-footed mouse hums.
          d.       The
white-footed mouse is very small.
5.       Which detail in paragraph 2 is interesting, but not needed to
find the main idea of that paragraph?
          a.       Its tail is 3
inches (7.5 cm) long.
          b.       Scientists
found 40-million-year-old fossils of its ancestors.
          c.       It weighs 0.8
ounces (23 g).
          d.       Its body is
about 8 inches (20 cm) long.

Practice 2: Dietary Details

Read the selection, andthen
answer the questions that follow.
(1)     Everyone needs food as fuel for his or her body. But kids
especially need the right fuel to keep their bodies going as they’re growing.
To help everyone figure out which foods supply the energy needed, the U.S.
Department of Agriculture (USDA) developed a new Food Guide Pyramid in 2005.
Look at the visual.
(2)     You probably remember the old pyramid, with horizontal layers of
blocks like the ancient pyramids. Well, this new pyramid has six, tall,
vertical stripes instead. Each stripe represents one source of nutrition. There
are horizontal steps on the side of the pyramid, but they signify the need for
exercise as well as good food—30 minutes of exercise a day—to create a healthy
(3)     This new pyramid is called MyPyramid, because it’s supposed to
help meet the needs of each individual. Your food needs are based on your age,
if you’re a girl or boy, and how active you are. You can go to the USDA website
at to check out how much and which kinds of food you need.
(4)     Each stripe on MyPyramid is a different color:
Orange: grains The average kid
needs 6 ounces a day from this group, which includes breads, cereals, rice, and
Green: vegetables The average
kid needs about   cups a day from this
group, which includes dark green veggies, like spinach and broccoli, and bright
orange ones, like carrots.
Red: fruits The average kid
needs about   2 cups of fresh, frozen,
canned, or dried fruit a day.
Yellow: oils Kids need about 5
teaspoons of oil a day. Some have no cholesterol or are lower in fat than
others. Check food labels for information.
Blue: milk The average kid
needs about 3 cups a day of milk, yogurt, or cheese.
Purple: meat, fish, beans, and
nuts The average kid needs about 5 ounces a day from this group.
(5)     These provide a “healthy diet.” That’s one that has
enough of each essential nutrient; a variety from all food groups; energy to
maintain a healthy weight; and no excess fat, sugar, or salt. Eating healthy
and exercising daily can help reduce the risk of getting diabetes, cancer, or
bone problems as you get older.
6.       Which is the most likely main idea of this selection?
          a.       People need
to exercise at least once a week.
          b.       Beans are a good
source of vitamins.
          c.       People need
to eat a variety of good foods and exercise for a healthy life.
          d.       Fiber is an
important part of a healthy lifestyle.
7.       Which is NOT a supporting detail for the main idea?
          a.       Always use
sunscreen as protection from the sun’s harmful rays.
          b.       Pick a
variety of things from the vegetable group.
          c.       Get at least
a half-hour of exercise every day.
          d.       Don’t just
pick foods from one food group.
8.       Why was it suggested that someone go to the USDA website?
          a.       to check the
local weather
          b.       to write a
letter to Congress
          c.       to exchange
recipes for wholesome, healthy foods that taste good
          d.       to find out
exactly which foods and how much that individual should eat
9.       Which would best be another title for the article?
          a.       The Nutrition
Needs of Prehistoric Humans
          b.       Food for
          c.       The Eating
Habits of Senior Citizens
          d.       Thoughts
about Work Routines
10.     Which is the main idea of the last paragraph?
          a.       It’s nice to
choose a variety of foods.
          b.       Many older
people have heart problems.
          c.       Eating right
and exercising now can reduce health risks in the future.
          d.       Getting
enough sleep is important to good health.

Practice 3: Radio Days

Read the selection, and then
answer the questions that follow.

(1)     Before there was TV, Americans gathered around their radios
daily to listen to the news and more. In the 1930s and 1940s, mystery shows,
like Sam Spade and The Shadow, were favorites with young and old alike. Every
week people tuned in to hear the top tunes on Your Hit Parade. And on Sunday
mornings, radio stars read the comics aloud to kids.
(2)     Did you think soap operas were a TV phenomenon? No way! They
started on radio. Do you know why they were called “soap operas”?
Most shows were sponsored by soap companies and, because characters had many
problems, people said the stories were like operas, most of which don’t have
happy endings!
(3)     Because there were no pictures to show what was going on, radio
required people to use their imaginations. So, as a sportscaster described the
action, people had to imagine “he hits a pop fly high into the infield,
the shortstop moves in . . . reaches . . . grabs it . . . throws to second . .
. and he’s out!” Not only did they picture it, many people cheered as if
they were right there in the stadium!
11.     Which best states the main idea of the article?
          a.       Soap operas
started on TV.
          b.       Before there
was TV, people listened to the radio a lot.
          c.       Quite often,
operas don’t end happily.
          d.       Top tunes
were played on the radio.
12.     The author says radio required people to use their imaginations
          a.       radio stars
read the comics.
          b.       people
cheered as if they were at the stadium.

          c.       The Shadow
was a mystery show.

          d.       there were no
pictures to show the action.
13.     Which could the author best use as another supporting detail?
          a.       Television
was not in many American homes until the 1950s.
          b.       Many cars did
not have a radio.
          c.       The modern
home has two or more TVs.
          d.       Two-way
radios were important during the war.