Working systematically

There are three tables in a room with blocks of chocolate on each. Where would be the best place for each child in the class to sit if they came in one at a time?

Arrange the four number cards on the grid, according to the rules, to make a diagonal, vertical or horizontal line.

Ten cards are put into five envelopes so that there are two cards in each envelope. The sum of the numbers inside it is written on each envelope. What numbers could be inside the envelopes?

On the graph there are 28 marked points. These points all mark the vertices (corners) of eight hidden squares. Can you find the eight hidden squares?

Can you make doughnuts by matching these fractions, decimals and percentages?

These points all mark the vertices (corners) of ten hidden squares. Can you find the 10 hidden squares?

Solve this Sudoku puzzle whose clues are in the form of sums of the numbers which should appear in diagonal opposite cells.

A Sudoku with clues given as sums of entries.

In this interactivity each fruit has a hidden value. Can you deduce what each one is worth?

Can you use the clues to complete these 5 by 5 Mathematical Sudokus?