Working systematically

I added together some of my neighbours' house numbers. Can you explain the patterns I noticed?

In this game you are challenged to gain more columns of lily pads than your opponent.

Investigate the different ways that fifteen schools could have given money in a charity fundraiser.

Can you arrange the digits 1, 1, 2, 2, 3 and 3 to make a Number Sandwich?

Place the 16 different combinations of cup/saucer in this 4 by 4 arrangement so that no row or column contains more than one cup or saucer of the same colour.

This challenging activity involves finding different ways to distribute fifteen items among four sets, when the sets must include three, four, five and six items.

A challenging activity focusing on finding all possible ways of stacking rods.

Can you put the 25 coloured tiles into the 5 × 5 square so that no column, no row and no diagonal line have tiles of the same colour in them?

Can you find numbers between 100 and 999 that have a middle digit equal to the sum of the other two digits?