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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}.

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Common Divisor

Find the largest integer which divides every member of the following sequence: 1^5-1, 2^5-2, 3^5-3, ... n^5-n.

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Hypotenuse Lattice Points

The triangle OMN has vertices on the axes with whole number co-ordinates. How many points with whole number coordinates are there on the hypotenuse MN?

There's Always One Isn't There

Age 14 to 16 Challenge Level:

Try plenty of examples :

Maybe start with other numbers and take multiples but continue dividing by 9.

Next use other numbers again, taking multiples of each as before but now divide by 7.

Then again use different numbers, take multiples and divide by 8 - be sure to include 12 as on of the numbers you try multiples of.

What happens?