Simultaneous equations

problem

Pareq Calc

Age

14 to 16

Challenge level

Triangle ABC is an equilateral triangle with three parallel lines going through the vertices. Calculate the length of the sides of the triangle if the perpendicular distances between the parallel lines are 1 unit and 2 units.
problem

Walls

Age

16 to 18

Challenge level

Plane 1 contains points A, B and C and plane 2 contains points A and B. Find all the points on plane 2 such that the two planes are perpendicular.
problem

Colour Islands Sudoku

Age

11 to 14

Challenge level

An extra constraint means this Sudoku requires you to think in diagonals as well as horizontal and vertical lines and boxes of nine.
problem

Addition Equation Sudoku

Age

11 to 14

Challenge level

You need to find the values of the stars before you can apply normal Sudoku rules.
problem

The Simple Life

Age

11 to 14

Challenge level

The answer is $5x+8y$... What was the question?
problem

Not a Polite Question

Age

11 to 14

Challenge level

When asked how old she was, the teacher replied: My age in years is not prime but odd and when reversed and added to my age you have a perfect square...
problem

Whole Numbers Only

Age

11 to 14

Challenge level

Can you work out how many of each kind of pencil this student bought?
problem

Intersection Sudoku 2

Age

11 to 16

Challenge level

A Sudoku with a twist.
problem

Quadruple Clue Sudoku

Age

11 to 16

Challenge level

Four numbers on an intersection that need to be placed in the surrounding cells. That is all you need to know to solve this sudoku.
problem

Another Quadruple Clue Sudoku

Age

11 to 16

Challenge level

This is a variation of sudoku which contains a set of special clue-numbers. Each set of 4 small digits stands for the numbers in the four cells of the grid adjacent to this set.