TOPICS
This page:
number sense,
about numbers
Search
Dr. Math
See also the
Dr. Math FAQ:
number glossary
and
integers,
rational numbers,
irrational numbers
and
large numbers
and infinity
and
prime numbers
and
square/cube roots
Internet Library:
number sense
MIDDLE SCHOOL
About Math
Algebra
equations
factoring expressions
graphing equations
Arithmetic
division
exponents
factorials
factoring numbers
fractions/percents
logarithms
Definitions
Geometry
2dimensional
conic sections/
circles
triangles/polygons
3D and higher
polyhedra
History/Biography
Logic
Measurement
calendars/
dates/time
temperature
terms/units
Number Sense
factoring numbers
negative numbers
pi
prime numbers
square roots
Probability
Puzzles
Ratio/Proportion
Statistics
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.
 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 Are All Repeating Decimals Classified Rational? [11/12/1997]

Please explain how .6 repeating can be a rational number when expressing
it over 10's, 100's, etc.
 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 does 0 factorial equal 1? [03/18/1998]

Why does 0! = 1? Is this like anything to the power of 0 equals 1?
 Why Do We Have Leap Year ? [02/25/1998]

Why do we need to have one extra day each 4 years?
 Why Do We Need to Study Rational Numbers? [04/22/2008]

My students want to know why they need to know what rational numbers
are and what use they have in the real world.
 Why Do We Use Order of Operations? [09/18/2008]

Why is it necessary to use order of operations? Why can't you just
write a calculation from left to right, so 5+2^3*2 is just 2^3*2+5?
Doctor Peterson shows how order of operations makes writing and
understanding algebraic expressions quite simple.
 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 Estimate? [09/16/2002]

Why do we use estimation?
 Why is 1 Not Considered Prime? [3/20/1995]

Just recently a grade six student asked me, "Why is 1 not considered
prime?" I tried to answer, but as usual, could not since I do not
understand this either. I thought the answer might lie in the fact that
we aren't using the true definition or we are interpreting it wrong.
 Why is Zero Not a Natural Number? [03/14/2001]

Can you explain why the natural numbers are {1, 2, 3...}? Also, is there
a way to prove that zero is an integer?
 Why Not Force Dividing by Zero? [10/22/2002]

Has there ever been an attempt to force dividing by zero just as it
has been done so successfully by forcing the square root of 1 to be
i?
 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 Use Q and Z? [09/12/2001]

Why is the letter Q used for rational numbers and Z for integers?
 Wondrous Numbers [02/07/2001]

What is a wondrous number?
 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?
 Working with Different Bases [9/7/1995]

Please explain base 10 to me  then base 4.
 Working with Sequences [11/14/1998]

Give the next two terms of the sequence: 1, 1, 2, 4, 3, 9, ....
 Would Aliens Use Base 10? [05/13/2002]

If aliens had 6 fingers, would they use base 12?
 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 One, Each Unique in Its Own Special Way [04/10/2013]

Zero is neither positive nor negative; 1 is neither prime nor composite. So how do we
classify these numbers?
 Zero and the Commutative Property of Multiplication [04/18/2003]

If we take 0x1, we get 0, and if we take 0x2, we still get 0, for it
is still 0+0+0. But if we do it the other way round, why must it
still be 0, if any number to the power of 0 = 1?
 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 in the Denominator [8/14/1996]

What is the value of 4/0 * 0/4?
 Zero Significance [10/27/2013]

Confused about the significance of the zeros on either side of a number such as
0.000, a student expresses doubts about manipulating them, and about representing
integers in scientific notation. Doctor Peterson clears the air.
Page: [<prev]
1
2
3
4
5
6
7
8
9
10
11
