Different by One
Age 14 to 16
Challenge Level 
In the original example, the lines were made from rods that differed in length by 2:
light green rods (3) and yellow rods (5).
You could start by creating lines made from
pink (4) and dark green (6)
yellow (5) and black (7)
yellow (5) and black (7)
dark green (6) and brown (8)
black (7) and blue (9)...
black (7) and blue (9)...
Which pairs can be used to create lines that differ by 1?
You may also like
DOTS Division
Take any pair of two digit numbers x=ab and y=cd where, without loss of generality, ab > cd . Form two 4 digit numbers r=abcd and s=cdab and calculate: {r^2 - s^2} /{x^2 - y^2}.
