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 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    2-dimensional      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. 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. Learning Addition and Multiplication with Algebra [3/16/1996] How do you know what the (a) is in algebra? I saw this on a picture: a(1/a) = 1/a(a) = 1... Page: []

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