How many intersections do you expect from four straight lines ? Which three lines enclose a triangle with negative co-ordinates for every point ?

Substitute -1, -2 or -3, into an algebraic expression and you'll get three results. Is it possible to tell in advance which of those three will be the largest ?

What does this number mean ? Which order of 1, 2, 3 and 4 makes the highest value ? Which makes the lowest ?

Take a few whole numbers away from a triangle number. If you know the mean of the remaining numbers can you find the triangle number and which numbers were removed?

In this short problem, try to find the location of the roots of some unusual functions by finding where they change sign.

Match the descriptions of physical processes to these differential equations.

Solve these differential equations to see how a minus sign can change the answer

Two students found all of the odd ones out, and gave clear explanations of their reasoning. How many did you get right?

This article -useful for teachers and learners - gives a short account of the history of negative numbers.

This Sudoku problem consists of a pair of linked standard Suduko puzzles each with some starting digits