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Title: Math/Recreations - Fast Arithmetic Tips Three categories: defensive - know to check an answer, offensive - fast mental calculations, and math magic.
Fibonacci_numbers_and_the_Pascal_triangle The relation between Fibonacci numbers and Pascal's triangle. English/German/Serbian.

Final_Answers Numerous facts including formulas, magic tricks, fallacies, recreations compiled by Dr. Gerald P. Michon.

Fun_With_Mathematics Includes pages on the topics of primes, fibonacci numbers, PI computation, data encryption and links to calculator programs.

Gardner_Index Rough index to the fifteen books containing Martin Gardner's Mathematical Games articles from Scientific American.

Geometric_Packing_Problems By Joseph Malkevitch: "Given one shape X how and when can one pack identical copies of this shape into another shape Y?"

HAKMEM A collection of problems from MIT. Work reported herein was conducted at the Artificial Intelligence Laboratory, a Massachusetts Institute of Technology research program.


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Fast Arithmetic Tips

Mental math - the skills of calculating fast - might be classified into three broad categories. Offensive.The purpose is getting the result fast. Example: Compute 47·53. Answer: 502 = 2500, 32 = 9. Therefore 47·53 = 2500 - 9 = 2491. Defensive.The purpose is to quickly establish implausibility of a result. Example: compute 91·18.Answer: 91·18 = 1538. This is obviously wrong because 18 is divisible by 9 and so must be the product 91·18.On the other hand, 1538 is not divisible by 9 since its digits sum up to 1 + 5 + 3 + 8 = 17 which is not divisibleby 9. The correct answer is 1638.Entertaining.The purpose is to stun with the ability to produce a result as much as with the result itself.Example: Think of a 3-digit number. Write it in reverse. Subtract the smaller of the two from the larger one. Give me the first two digits of the result. I'll respond with the remaining digit.

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Calculation Tips & Tricks Copyright © 1996-2008 Alexander Bogomolny30872388Page copy protected against web site content infringement by Copyscape addthis_url = location.href; addthis_title = document.title; addthis_pub = ''; CiteThisPageAs();_uacct = "UA-358853-1";urchinTracker(); Search: All Products Apparel Baby Beauty Books DVD Electronics Home & Garden Gourmet Food Personal Care Jewelry & Watches Housewares Magazines Musical Instruments Music Computers Camera & Photo Software Sports & Outdoors Tools & Hardware Toys & Games VHS Computer Games Cell Phones Keywords: srExecute(); Amazon.com Widgets Latest on CTK Exchange Grade 4 math??? Posted by viking1 1 messages 04:40 PM, Dec-01-08 Help me find Hisashi ABE, Pythago ... Posted by likesmath 2 messages 11:11 AM, Oct-06-08 Bearing problem Posted by Liliya 3 messages 11:32 AM, Nov-27-08 What is the smallest rational sqr ... Posted by MinusOne 4 messages 04:32 PM, Nov-27-08 Three Concurrent Circles Posted by billmillar 2 messages 12:26 PM, Oct-28-08 Ant on Dicube (error?) Posted by Pierre Charland 1 messages 08:58 PM, Dec-01-08 Error in Fractal Curves and Dimen ... Posted by miguemate22 1 messages 08:51 AM, Nov-16-08 Amazon.com Widgets
 

Three

categories:

defensive

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know

to

check

an

answer,

offensive

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fast

mental

calculations,

and

math

magic.

http://www.cut-the-knot.com/arithmetic/rapid/index.shtml

Fast Arithmetic Tips 2008 December

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Three categories: defensive - know to check an answer, offensive - fast mental calculations, and math magic.

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