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The Triangle Where Numbers Add Up

4th grade nonfiction passage about number patterns in a triangle: 188 words, six questions, an answer key and vocabulary.

4th grade nonfiction number patterns in a triangle 188 words

The Triangle Where Numbers Add Up

Some number patterns hide in plain sight. One of the most famous looks like a triangle made of numbers. It is called Pascal's triangle, named for a French mathematician who studied it. People in other parts of the world knew about it long before him.

Start at the top with a single 1. The next row has two 1s. Now comes the rule. To build any new row, begin and end with 1. Every number in the middle is made by adding the two numbers just above it.

Try it. The third row is 1, 2, 1, because 1 plus 1 makes 2. The fourth row is 1, 3, 3, 1. The fifth row is 1, 4, 6, 4, 1. Check the 6. The two numbers above it are 3 and 3, and they add up to 6.

The triangle holds surprises. Add up each row. You get 1, then 2, 4, 8, and 16. Each total is double the one before it. Look along the edge, just inside the 1s. You find the counting numbers 1, 2, 3, 4, and so on.

You do not need to be a famous mathematician to explore it. With a pencil, a sheet of paper, and one simple rule, you can keep growing the triangle forever and keep finding new patterns.

Questions

  1. What is the triangle in this passage called? in the text

  2. How do you make a number in the middle of a row? in the text

  3. What numbers are in the fifth row? in the text

  4. What happens when you add up each row? in the text

  5. Why does the passage say people in other parts of the world knew about the triangle? think about it

  6. What do you need to keep growing the triangle? in the text

Words to know

pattern
numbers or shapes that repeat by a rule
mathematician
a person who studies numbers and shapes
middle
the part that is between the two ends
double
two times as much
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One passage, three levels

The same topic and facts written three ways, so a mixed class can read and talk about one text. Each group’s sheet shows only a shape; the key says which is which.

● Easier · 149 words · Flesch-Kincaid grade 2.2

Some number patterns hide in plain sight. One looks like a triangle made of numbers. It is called Pascal's triangle. It is named for a French mathematician who studied it. People in other places knew it long before him.

Start with a single 1 at the top. The next row has two 1s. Here is the rule. Every new row begins and ends with 1. Each number in the middle is made by adding the two numbers just above it.

Try it. The third row is 1, 2, 1, because 1 plus 1 is 2. The fourth row is 1, 3, 3, 1. The fifth row is 1, 4, 6, 4, 1. Check the 6. The two numbers above it are 3 and 3. They add up to 6.

The triangle has surprises. Add up each row. You get 1, 2, 4, 8, and 16. Each one is double the last. Look just inside the 1s. You will see 1, 2, 3, 4, the counting numbers.

You only need a pencil, paper, and one rule to keep growing it.

▲ This passage · 188 words · Flesch-Kincaid grade 3.3

Some number patterns hide in plain sight. One of the most famous looks like a triangle made of numbers. It is called Pascal's triangle, named for a French mathematician who studied it. People in other parts of the world knew about it long before him.

Start at the top with a single 1. The next row has two 1s. Now comes the rule. To build any new row, begin and end with 1. Every number in the middle is made by adding the two numbers just above it.

Try it. The third row is 1, 2, 1, because 1 plus 1 makes 2. The fourth row is 1, 3, 3, 1. The fifth row is 1, 4, 6, 4, 1. Check the 6. The two numbers above it are 3 and 3, and they add up to 6.

The triangle holds surprises. Add up each row. You get 1, then 2, 4, 8, and 16. Each total is double the one before it. Look along the edge, just inside the 1s. You find the counting numbers 1, 2, 3, 4, and so on.

You do not need to be a famous mathematician to explore it. With a pencil, a sheet of paper, and one simple rule, you can keep growing the triangle forever and keep finding new patterns.

■ Harder · 213 words · Flesch-Kincaid grade 6.7

Certain number patterns hide in plain sight, and one of the most famous resembles a triangle constructed entirely from numbers. It is called Pascal's triangle, in honor of a French mathematician who studied it carefully, although people in other parts of the world had known about it long before he did.

Begin at the top with a single 1. The next row contains two 1s. Now comes the important rule. To build any new row, you start and finish with 1, and every number in the middle is produced by adding together the two numbers directly above it.

Try it yourself. The third row is 1, 2, 1, because 1 plus 1 equals 2. The fourth row is 1, 3, 3, 1, and the fifth row is 1, 4, 6, 4, 1. Check the 6 to be sure. The two numbers above it are 3 and 3, and together they make 6.

The triangle is full of surprises. If you add up every row, you get 1, then 2, 4, 8, and 16, and each total is double the one before it. If you look along the edge, just inside the 1s, you discover the counting numbers 1, 2, 3, 4, and so on.

You do not have to be a famous mathematician to explore it. With only a pencil, a sheet of paper, and one simple rule, you can keep growing the triangle forever and continue finding new patterns as you go.

Download as one PDF

How to use it

  1. Press Read it big (or B) to put the text on the projector, or Full screen (F) to fill the whole screen.
  2. Ask the questions one at a time and use Show answer when the class has decided. A shows or hides every answer.
  3. Print student copy for the class, or Print with answers for yourself.

Ideas for class

  • Before reading, put pattern, mathematician, middle and double on the board with their meanings from the Words to know section and have students predict what the text will be about.
  • Read it aloud once while students follow along, then have them reread it alone or with a partner. At a calm 100 words a minute it takes about 2 minutes to read aloud.
  • Use the Read it big button (or B) to put the text on the projector, and Show answer on one question at a time so the class commits to an answer first.
  • Question 5 asks the reader to infer. Ask students to point to the words in the passage that led them to their answer.
  • Ask students to write one question the passage did not answer, then look for the answer in a book or on a classroom screen.
  • Print the student copy for independent work and keep the answer-key copy for yourself.

Related

Questions

What reading level is "The Triangle Where Numbers Add Up"?

It was written for 4th grade. It has 188 words and works out to a Flesch-Kincaid grade level of about 3.3. That is a formula's estimate from sentence length and syllables, and it is not a Lexile or a guided reading level, so check it against your students.

What do the questions ask?

There are six. 5 ask for something the text says directly and 1 ask the reader to work something out from clues. Each has an answer in the key, and the answers are written as a teacher would accept them, not as the only possible wording.

How long does it take to read?

About 2 minutes read aloud at 100 words a minute. For a one-minute fluency check, paste it into the fluency timer and use the word count.

Can I print it?

Yes. Print student copy gives the passage, the questions with lines to write on, and the word meanings. Print with answers gives the same page with the answers filled in. Both are made in your browser.

Is this passage from a published book?

No. It was written for Peabody Teach, so there is no book to buy and no login to read it.

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