The Math Forum

Ask Dr. Math

Middle School Archive

Dr. Math Home || Elementary || Middle School || High School || College || Dr. Math FAQ

This page:
  number sense,
  about numbers checkmark

  Dr. Math

See also the
Dr. Math FAQ:
  number glossary
  rational numbers,
  irrational numbers
  large numbers
  and infinity
  prime numbers
  square/cube roots

Internet Library:
  number sense


About Math

   factoring expressions
   graphing equations

   factoring numbers


     conic sections/
   3D and higher



Number Sense
   factoring numbers
   negative numbers
   prime numbers
   square roots

Word Problems

Browse Middle School 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.
    Significant figures/digits.

The Imaginary Number [1/5/1995]
A student questions the meaning of the imaginary number, i.

Imaginary Numbers [02/28/1999]
What jobs and professions use imaginary numbers?

The Importance of Number Sense and Estimating Answers [04/28/2004]
I don't understand how to solve problems using number sense. For example, if an employee at the deli counter slices a 2 foot long salami, about how many slices will he get? How can I figure that out? Why is it important?

Inequalities on a Number Line [05/07/2003]
How do you graph inequalities on a number line?

Infinite Number of Primes [04/14/1998]
Prove there are an infinite number of primes. What is the largest prime number known?

Infinity [5/24/1996]
Is infinity positive or negative?

Infinity and Inequalities [06/05/2002]
I'm supposed to use positive and negative infinity to solve problems like 2x - 3 < 7.

Infinity minus Infinity [10/26/1995]
Infinity - Infinity = ?

Infinity Plus One [12/26/1995]
What is infinity plus one?

Infinity times Infinity [10/15/1998]
What is infinity multiplied by infinity?

Integers and Rational Numbers [5/25/1995]
Can you explain the difference between SET Q (rational numbers) and SET Z (integers)?

Integers in Everyday Life [01/16/2002]
How do we use integers in everyday life?

Introduction to Rational Numbers for Middle School Students [12/06/2006]
Why do we need to know about rational numbers? Aren't all fractions rational numbers? What's the difference?

Irrational Between Two Rationals [07/19/2002]
How can I find an irrational number that lies between a pair of rational numbers?

Irrational Numbers [08/13/1997]
How can three irrational numbers added together give you a rational number?

Irrational Numbers [01/07/1998]
Are pi and the square root of 2 irrational numbers? Why? What about 1.33333... and 1.181818...?

Irrational Numbers [01/13/1998]
How do you prove that (sqrt)2 is irrational? Given two irrational numbers, a and b, is it possible to get an a^b that is rational?

Irrational Numbers; Rational Square Roots [02/04/1998]
How can you tell whether root 10 is a terminating or repeating decimal, or an irrational number? Are some square roots rational?

Irrational Pi [7/15/1996]
Why is pi considered an irrational number when it's defined as the ratio of the circumference of a circle to its diameter?

Irrationals and Their Representations, Decimal and Otherwise [05/09/2015]
A teacher wonders if the non-terminating decimal expansions of SQRT2 and pi reveal some inadequacy about the base ten number system — or her overreliance on it. Expanding on her question, Doctor Peterson discusses the limitation of any human representation.

Is 0 a whole number? [7/17/1996]
Is 0 a whole number?

Is Integer Division Associative? [05/14/2002]
Is integer division associative?

Is It Possible That x/0 is Not Really Undefined? [06/14/2004]
Is it possible that 1/0 is not really undefined, but is in fact the key to a whole new class of numbers, much as the imaginary unit i led to the development of complex numbers?

Isn't 1/0 the Biggest Number? [02/28/1998]
It makes sense that if you add or multiply a number to the biggest number you will get the same biggest number, right?

Is One a Triangular Number? [03/22/2004]
Triangular numbers have that name because if drawn as dots they can form a triangle. But 1 is just a single dot, so it can't be a triangular number, can it?

Is Pi Infinite? [01/29/1998]
How can we know that pi is infinite? Does it ever turn into a pattern of zeros and ones, like a computer code?

Is Zero a Multiple of Every Number? [07/06/2002]
Is zero a multiple of every number? I have some books that say it is, and others that say it isn't.

Is Zero a Number? [10/23/1995]
Why is 0 classified as a whole number and not a natural number? Natural numbers can be touched, whereas whole numbers cannot - is 0 a whole number strictly by definition?

Is Zero a Number? [07/05/2003]
If infinity is not a number, then is zero really a number?

Is Zero a Signed Number? [01/09/2002]
What is the sign of zero?

Is Zero a Square Number? [02/16/2000]
Is zero considered to be a square number? I have found some sources that say it is, and others that say it isn't.

Is Zero Even? [03/28/2001]
The justification that 0 is an even number is based on the fact that 0 is divisible by 2. But how many times does 2 go into 0? Answer: no times; or to rephrase, 2 doesn't go into 0. Can you explain this?

Is Zero Even, Odd, or Neither? [03/31/1997]
Two students bet on whether zero is even, or neither even nor odd.

Is Zero Odd or Even? [06/17/1998]
My 4th grade students are not satisfied with any explanation I can offer.

Is Zero Prime or Composite? [10/23/1995]
Is zero prime, composite, or neither?

Is Zero Really a Number or Just a Concept? [09/15/2005]
I've been taught that infinity is just a concept, not an actual number. I'm wondering if the same thing can be said of zero?

Karatsuba Multiplication [10/15/2007]
Can you explain the ideas and steps behind the Karatsuba method of multiplying?

K as an Abbreviation for Thousands [05/29/2002]
I was taught that 30K meant thirty thousand. Is that correct?

Laps and Least Common Multiples [05/24/2002]
Three people are running around a track at different speeds. When will they all return to the starting point at the same time?

The Last Finite Number? [02/01/2004]
I just read an article about the "last finite number", and I was wondering whether such a number could possibly exist.

Page: [<prev]  1  2  3  4  5  6  7  8  9 10 11 [next>]

Search the Dr. Math Library:

Search: entire archive just Middle School Number Sense/About Numbers

Find items containing (put spaces between keywords):
Click only once for faster results:

[ Choose "whole words" when searching for a word like age.]

all keywords, in any order at least one, that exact phrase
parts of words whole words

[Privacy Policy] [Terms of Use]

Home || The Math Library || Quick Reference || Search || Help 

© 1994- The Math Forum at NCTM. All rights reserved.