See also the
Dr. Math FAQ:
0.9999 = 1
0 to 0 power
n to 0 power
0! = 1
dividing by 0
Browse High School Number Theory
Stars indicate particularly interesting answers or
good places to begin browsing.
Selected answers to common questions:
Infinite number of primes?
Testing for primality.
What is 'mod'?
- 0 Divided by 0 [11/27/1997]
What is the answer to 0 divided by 0? I think it is undefined...
- 100 Factorial in Base 6: How Many Zeros? [10/24/2001]
How many zeros are there at the end of 100! in base 6?
- Adding Arithmetic Sequences [07/10/1998]
How do you add the numbers from 1 to 5000 without actually doing it or
using a calculator? What if you were adding just the odd numbers?
- Adding Hexadecimals [07/13/1998]
A complete introduction to the hexadecimal, including sample problems on
- Adding in Base 9 and Base 5 [10/21/1997]
In 3rd grade my son is learning how to add in bases other than 10.
- Arithmetic in Other Bases [02/25/2002]
I need to know how to write out the steps for addition, subtraction,
multiplication, and division in other bases.
- Base 12 Fractions [11/05/2001]
I need a simple way to understand how to do and interpret decimals in
- Base 26 [01/27/1997]
In a base 26 number system where the letters of the alphabet are the
digits, calculate TWO+TWO in this system and express the answer in base
ten. Express 1997 in base 26.
- Base 2 Subtraction and Clock Arithmetic [01/26/2001]
We know that computers use the "2's complement" method to do subtraction
of base 2 numbers, and that this method works every time, but we have no
idea why it works.
- Base Number [10/07/1998]
What does base number mean?
- Base Number Equivalence Tables [10/30/2001]
My son needs to show tables for base 3 and base 7.
- Binary Conversion [01/07/1998]
In an adult computer course we are supposed convert binary numbers to
real numbers and binary to hexadecimal.
- Binary Subtraction [7/25/1996]
I understand the rules of adding in binary, but how in the world do you
- Binary Subtraction [07/04/2003]
I need help understanding the rules of subtracting binary numbers when
the subtrahend is larger then the minuend.
- Binary System [5/22/1996]
How do you use the binary system?
- Calculating the Last Digit of an ISBN Number [07/15/1998]
How do you calculate the last number in an ISBN number?
- Calculator Addition [6/30/1996]
How does a calculator add?
- Cardinal and Ordinal Numbers [01/08/1997]
How can 3 be both a cardinal and ordinal number at the same time?
- Classifying Numbers [09/06/2001]
Can you tell me about complex numbers, real and imaginary numbers,
rational/irrational numbers? I don't understand any of it.
- Concepts of Adding in Base 2 [08/18/1998]
I don't understand the whole concept of base 2.
- Congruum Problem [04/04/2002]
I have found a reference to Fibonacci and his congruum problem. But
something has me stumped...
- Converting from Base 6 to 10 and Back [09/26/2001]
I need to know how to convert 2411 in base 6 to base 10.
- Counting: Base 6, 12, 16 [5/31/1996]
How do you count in base 6 and base 12? What about base 16?
- Decimal To Fraction Conversion [06/25/1998]
I am trying to find a method (one that can be programmed on a PC) to
convert the decimal part of a real number to a fraction represented by
integers for the numerator and denominator.
- Defining Kinds of Numbers [03/21/1997]
Could you please define: perfect numbers, deficient numbers, square
numbers, abundant numbers, amicable numbers, and triangular numbers?
- Definition of the Signum Function [05/31/2000]
Can you give me a simple definition of the signum function, and any
practical examples of its usage?
- Diagram for Math Numbers [10/05/1997]
My daughter is doing a tree diagram using terms related to math
"numbers." Could you please explain in lay terms what surds are?
- Difference Between Zero and Nothing [12/12/1996]
What is the difference between zero and nothing?
- Divide by 0 Undefined? [9/10/1996]
When something is divided by 0, why is the answer undefined?
- Dividing by 9, 99, 999.... [9/7/1996]
Please explain why dividing x by n 9's (x/99, for example) yields a
sequence of n repeating digits.
- Divisor Counting [9/24/1995]
A student asks a question about the Math Forum Problem of the Week.
- Erdos' Proof of Bertrand's Postulate [3/23/1997]
I am looking for a proof of Bertrand's Postulate (there exists a prime
number between n and 2n (n>2)), a.k.a. Chebychev's Theorem.
- Even + Even = Even [11/06/2001]
Prove that an even number + an even number = an even number.
- Fermat's Last Theorem - Disproof? [05/09/1998]
I would like to ask you whether there is any problem with the following
disproof of Fermat's last theorem...
- Fermat's Last Theorem: Explanation [11/02/1997]
Please give me some information on Fermat's Last Theorem.
- Finding and Factoring Large or Mersenne Primes [02/22/1998]
How do you find extremely large primes (Mersenne Primes) and how do you
tell if they are prime? What is the most efficient way of factoring
- First Ten Perfect Numbers [12/11/2001]
I have to figure out at least 10 perfect numbers for my homework.
- Fraction/Decimal Conversion to Other Bases [08/12/1998]
What are the rules for converting fractions to binary and octal and vice
- Frequency of Primes [03/17/1997]
Is there a pattern to describe the frequency of prime numbers?
- How can .999999.... equal 1? [03/21/2001]
If .99999999.... goes on forever, wouldn't it be just a little below one?