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 TOPICS This page:   place value    Search   Dr. Math See also the Dr. Math FAQ:   rounding numbers T2T FAQ:   place value help ELEMENTARY Arithmetic    addition    subtraction    multiplication    division    fractions/decimals Definitions Geometry    2-dimensional      circles      triangles/polygons    3D and higher      polyhedra Golden Ratio/ Fibonacci Sequence History/Biography Measurement    calendars/      dates/time    temperature    terms/units Number Sense/ About Numbers    infinity    large numbers    place value    prime numbers    square roots Projects Puzzles Word Problems Browse Elementary Place Value Stars indicate particularly interesting answers or good places to begin browsing. Selected answers to common questions:     Place value questions.     Rounding numbers.     Scientific notation.     Significant figures/digits. Scientific Notation of Zero [09/09/2002] What is the scientic notation of zero? Significant Digits [09/07/1998] What are significant digits? Significant Digits and Irrational Numbers [09/24/2005] How can you determine the signifigant digits of a non-terminating or irrational number like pi? Significant Digits and Zero [05/19/1999] When are zeros significant and when are they not significant? Significant Digits in Measurement [08/13/2001] I understand that there are rules to determine the significant digits in measurement, but aren't all digits significant, especially zeros for place value? Significant Digits in Numbers Written in Scientific Notation [06/20/2005] A discussion between Dr. Peterson and a student who is struggling with how to determine significant digits in general and with regard to numbers in scientific notation in particular. Significant Figures [02/25/1999] Why does 62.3 * 5.7 = 360 and not 355? Significant Figures in 36 2/3 [11/06/2001] How many significant figures are there in the area "36 2/3 Acres"? Smallest 5-Digit Number [02/05/2002] My dad says the smallest 5-digit number is 00000, but my teacher says it is 10000. The dictionary says that zero is a digit. What's the right answer? Square Numbers End in 0 1 4 5 6 9 [10/15/2002] Why do all square numbers end in 0 1 4 5 6 9? Subtracting and Borrowing in a Column [09/05/2002] A student borrowed in a column as follows: 6.9 - 7.92, to get -2.98. Why won't borrowing work with this number? Subtracting Mixed Fractions With Borrowing [01/08/2004] Two methods for subtracting mixed fractions involving borrowing because the fraction being subtracted is larger than the other one. For example, 5 3/8 - 10 6/8. Subtracting with Mixed Units [02/10/2009] How would you subtract 1 ton, 12 lb, 6 oz from 4 tons? Truncating [01/19/2002] What does truncating mean? Use and Meaning of 'And' in Naming Decimals [12/01/2004] Can you please tell me what the word "and" means in the word form of a decimal number? Using Hyphens to Indicate Place Value [08/30/2004] What is the difference between "five hundred thousandths" and "five hundred-thousandths"? 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? Why Multiplying by 10 Just Adds a Zero at the End [10/18/2005] My 8-year old is having trouble understanding why multiplying by 10 just adds a 0 to the end of the number. Do you have any thoughts on how to explain it to her? Why the Decimal Point Moves when Multiplying by 10 [02/11/2005] I am trying to explain why when you multiply a number by 10 you move the decimal point over one place to the right, and one place to the left when you divide by 10. Working in Base 7 [08/02/2007] How do I add, subtract, multiply and divide in base 7? Working Up to Counting Up [09/25/2003] My daughter wants to learn how to make change by counting up. Writing Decimals from Words [10/05/1998] Given a decimal written in words, how do you turn it into a decimal? In other words, how do you turn the words into numbers? Writing Numbers in Words [09/15/1997] Write each number in words: 1) 73.78007 2) 2.900087 (3) 34.4939. Zeros after the Decimal Point [09/17/2001] I have a group of students who just can't comprehend my explanation of how 3.70 is equivalent to 3.7 or 3.700 or 3.7000. Page: [

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