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Browse Elementary Number Sense/About Numbers
Stars indicate particularly interesting answers or
good places to begin browsing.
Selected answers to common questions:
About zero.
Multiplying by zero.
Casting out nines.
Classifying numbers.
Googol, googolplex.
Number facts from the Web.
 What is 0? [5/21/1996]

Is 0 a positive or a negative integer, or neither?
 What is a Number Base? [04/19/2003]

The base eight number 7n3 is equal to the base 7 number 1n35.
What digit does n stand for?
 What is a Parenthesis? [07/17/2000]

What does the mathematical term "parenthesis" mean?
 What is Expanded Notation? [08/22/2001]

My daughter was asked to rewrite each number as expanded notation. What
is expanded notation?
 What is Number Sense and How Can You Improve It? [08/29/2007]

What does the term 'number sense' refer to on standardized math test
results? Is there any way to increase your number sense?
 Where Does Pi Come From? [11/04/1996]

If pi is a ratio of lengths that can be measured only so accurately, how
can we know the value of pi so exactly?
 Who Invented Integers? [11/29/2001]

And when were integers invented?
 Whole Numbers and Multiples [09/11/2001]

My students and I have been trying to figure out what numbers are in the
set of "Whole Numbers." Is zero a whole number?
 Why Casting Out Nines Works [10/13/2008]

Can you explain in simple terms why the Casting Out Nines method works?
 Why Commas after Every Three Places? [07/10/2001]

Why do we put commas after every three places in a number like 200,000?
 Why Estimate? [08/16/2002]

Estimate to the nearest thousand a solution to Dave's subtraction
problem. The numbers are: 6,107  2,980 = 4,127.
 Why Rules? [08/15/2001]

Why do we need to have rules for order of operations?
 Why Study Prime and Composite Numbers? [01/25/2001]

My husband and I wonder why this is taught in school at all. Who uses
this in the real world? Why does someone need to know whether a number is
a prime number or not?
 Why Two Odds Always Sum to an Even [03/21/2002]

Why do two odd numbers always equal an even number but two even numbers
never equal an odd number?
 Why Zero is neither Positive nor Negative [10/5/1995]

My class and I are wondering if 0 is a negative or a positive number and
why.
 Word for a 225th Birthday [07/10/2001]

This year America is celebrating its 225th birthday. As we celebrated the
bicentennial in 1976, is there a term for 225 years?
 Working in Base 7 [08/02/2007]

How do I add, subtract, multiply and divide in base 7?
 Writing Numbers [11/24/2002]

Which words are okay to capitalize and when are hyphens used between
words?
 Writing Numbers in Words [09/15/1997]

Write each number in words: 1) 73.78007 2) 2.900087 (3) 34.4939.
 Zero and Negative Infinity [06/02/2003]

What is the smallest number? Zero or negative infinity? Explaining
concepts to a fouryearold.
 Zero Before the Decimal Point? [10/06/2000]

What is the merit of writing the zero before the decimal point in numbers
less than one, for example 0.25?
 Zero for Children [03/16/2002]

When you are teaching children to count (110), do you include zero? Why
or why not? How do you explain to a child (K2) what the value of zero
is, and is zero just a place holder?
 Zero in the Denominator [8/14/1996]

What is the value of 4/0 * 0/4?
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