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Tuesday, June 30, 2015

Landmark Numbers: Focus 2


When you think of the number two, what do you think of; what do you know?

Students and I will discuss the question above as we continue to examine numbers 0-12 at the start of the year.

We're studying landmark whole numbers and fractions at the start of the year as one way to review the essential vocabulary, properties, models, and math tools that lay the foundation for the fifth grade math year.

As students share their knowledge of two we'll list words that define two, properties, number line location, and the way that two "behaves." Then students will complete this home study page to review the learning on their own at home.

Where does 2 sit on a number line.

-3______-2______-1______0______1______2______3

What words define two?
  • Two is an even number because 1 + 1 = 2. It has parity which means it can be split into two equivalent whole parts or numbers.  
  • Two is the only even prime number because it's the only even number that has one and only one factor pair: 1 X 2 = 2
  • Two is a one-digit number because it is made from only one digit: 2.
  • Two is a rational number because it can be written as a fraction: 2/1, 4/2
  • Two is a whole number because it names the quantity of two and has no fractional parts.
  • Two is a natural number because it is a positive whole number greater than 0.
  • Two is an integer because it is a whole number with fractional parts.
What words do not define two?
  • Two is not a negative number because it is greater than 0.
  • Two is not an odd number because it can be split into two even whole number parts.
  • Two is not a composite number because it has only one factor pair. 
  • Two is not an irrational number because it can be written as a fraction. 
  • Two is not a fraction because it is written as a whole number, but it can be written as a fraction.
How does 2 "behave."
  • When you add 2 to a number it becomes 2 more or "jumps" two whole numbers on the number line.
  • When you subtract two, you "jump" to the left on the number line and reduce the value of the number by 2.
  • The additive inverse of 2 is -2, and the absolute value of 2 and -2 is 2.
  • When you multiply by two, you double the number.
  • When you divide by two, you split a number in half.
  • All the multiples of 2 are even numbers.
  • All multiples of 2 end in 0,2,4,6,8.
  • Two and three are the only consecutive prime numbers.
  • Two is the base of the simplest numeral system: binary system used in computers 
  • The square root of two is the first known irrational number.
  • When you raise a number to the power of 2, you square that number or multiply the number by itself. When you draw an array of a squared number, the array is a square.

More questions about 2:

  • What does 2 look like in a tally?
  • What is the history of the glyph (picture) 2?