View source for Activities/Abacus/Worksheet/Answersheet

==Answers to the Abacus Worksheet==
===Ways to make 1/2===
Ways to make 1/2 just using one string

[[File:Abacus1of2.jpg]][[File:Abacus2of4.jpg]] [[File:Abacus3of6.jpg]] [[File:Abacus4of8.jpg]] [[File:Abacus5of10.jpg]] [[File:Abacus6of12.jpg]]

To make 1/2 just using one string, the fraction denominator must be divisible by 2. The string must contain an even number of beads, 2 4 6 8 10 12


Ways to make 1/2 with more than one string

1/3 + 1/6 = (2+1)/6 = 3/6 = 1/2

1/3 + 2/12 = (4+2)/12 = 6/12 = 1/2

1/4 + 1/6 + 1/12 = (3+2+1)/12 = 6/12 = 1/2

1/4 + 2/8 = (2+2)/8 = 4/8 = 1/2

1/4 + 3/12 = (3+3)/12 = 6/12 = 1/2

3/9 + 2/12 = (12+6)/36 = 18/36 = 1/2

2/8 + 3/12 = 1/4 + 1/4 = 1/2

1/6 + 4/12 = (2+4)/12 = 6/12 = 1/2

1/6 + 3/9 = (3+6)/18 = 9/18 = 1/2

1/6 + 2/8 + 1/12 = (4+6+2)/24 = 12/24 = 1/2

2/6 + 2/12 = (2+1)/6 = 3/6 = 1/2

1/5 + 3/10 = (2+3)/10 = 5/10 =1/2

2/5 + 1/10 = (4+1)/10 = 5/10 =1/2


Is this all of the possibilities?

See [http://en.wikipedia.org/wiki/Diophantine_equation Diophantine equations], computer programs [http://tonyforster.blogspot.com/2010/09/turtle-diophantine.html including ones written in TurtleArt] can find all the solutions by trial and error.

You can paste [[File:Turtle Art Activity fraction diophantine.ta |this code]] into Turtle Art to calculate all the possibilities

===Ways to make 1/3===
This program can be modified for 1/3 and 2/3 (and with more work it could be used for the Caacupé abacus). Circled below, the program above has 0.5 replaced with 1/3 to find the ways of making 1/3


4/12

3/9

2/8 + 1/12

1/6 + 2/12

2/6

1/4 + 1/12

1/3

===Other representations of fraction addition===
====Paint====

====Turtle Art====
Copy [[File:Turtle Art Activity pie.ta | this code]] into TurtleArt to generate the pie for 1/3 + 1/6