### Volume 2, Number 39

 ``` 29 September 1997 Vol. 2, No. 39 THE MATH FORUM INTERNET NEWS Keep Traffic Moving! | The Abacus | BEATCALC KEEP THE TRAFFIC MOVING! http://www.math.toronto.edu/mathnet/carcompet/carcompet.html Everybody knows how frustrating it is to sit at a red light. Worse, a light that stays red too long can cause cars to back up, leading to gridlock. It's the traffic engineer's job to time things so that cars do not have to wait too long. On this site, you are the traffic engineer. Through a computer simulation, you control the timings of the lights at six intersections. Each road has two lanes, one in each direction. You have measured the traffic densities and you know that traffic behavior follows a particular mathematical model (the model is described onsite). Your task: - decide whether traffic lights are even feasible; - find what happens when a long light of cars is waiting at a red light and the light turns green; - find the best light timings for three specific situations. You are invited to try your hand at exploring mathematics in action in this real life situation. The competition was held in 1996 by the Univ. of Toronto Mathematics Network. -|-\-/-|-\-/-|-\-/-|-\-/-|-\-/-|-\-/-|-\-/-|-\-/-|-\-/-|-\-/-|- THE ABACUS The Art of Calculating with Beads - Luis Fernandez http://www.ee.ryerson.ca:8080/~elf/abacus/ All about the abacus, a calculator whose earliest known use was c. 500 B.C. in China. The abacus was used by the Japanese beginning around 1600 A.D., and excavations have revealed an Aztec abacus, c. 900-1000 A.D., "where the counters were made from kernels of maize threaded through a strong that attached to a wooden frame." Site features: - Construction and anatomy, abacus basics - Proper finger technique - A Java applet representing the number 87,654,321 - Instructions for addition and subtraction - The Abacus vs. the Electric Calculator - The Japanese, Chinese, and Aztec abacus, compared - Resources: purchase an abacus or build one out of LEGO - Abacus Museum -|-\-/-|-\-/-|-\-/-|-\-/-|-\-/-|-\-/-|-\-/-|-\-/-|-\-/-|-\-/-|- BEAT THE CALCULATOR - BEATCALC! http://jjj.mega.net/BEATCALC/ A mailing list from B. Clay. Each Monday an email message is sent to more than 4000 subscribers, with an exercise that illustrates how to do mental math computations faster than with a calculator. Learn to square numbers made up of 9's; multiply a 2-digit number by 594 or 693; or divide a repeating 6-digit number by 7, 11, and 13, then subtract 101... and many more. More than 90 of these mental tricks have been archived by the Math Forum: http://mathforum.org/k12/mathtips/beatcalc.html -|-\-/-|-\-/-|-\-/-|-\-/-|-\-/-|-\-/-|-\-/-|-\-/-|-\-/-|-\-/-|- CHECK OUT OUR WEB SITE: The Math Forum http://mathforum.org/ Ask Dr. Math http://mathforum.org/dr.math/ Problem of the Week http://mathforum.org/geopow/ Internet Resources http://mathforum.org/~steve/ Join the Math Forum http://mathforum.org/join.forum.html Send comments to the Math Forum Internet Newsletter editors _o \o_ __| \ / |__ o _ o/ \o/ __|- __/ \__/o \o | o/ o/__/ /\ /| | \ \ / \ / \ /o\ / \ / \ / | / \ / \ ```