Math Forum Internet News

Volume 2, Number 39

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29 September 1997                                Vol. 2, No. 39


        Keep Traffic Moving! | The Abacus | BEATCALC

                  KEEP THE TRAFFIC MOVING!

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

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

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




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More than 90 of these mental tricks have been archived by 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:


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