Negative numbers is not one of my favourite topics to teach. Pupils often struggle to understand the differences between adding and subtracting integers and get fixated on rules such as “two negatives make a positive” and it can be a struggle to get pupils engaged.
One way I try and put some excitement into the topic is using a couple of activities from http://nrich.maths.org.
Here are two of my favourites:
I have a laminated set of game boards – pupils play in twos and the aim is to roll two dice then add or subtract to cover up a number on the game board. The aim of the game is to get three in a row, either vertically, horizontally or diagonally.
The game can be demonstrated on the board and after the pupils have been playing for a while we will stop and discuss strategies, observations, explanations and justifications of how best to win.
I have used a game board with a wider range of numbers and using 20 sided dice.
There is another version called Connect Three
which involves using dice with negative values on them. This allows for a range of adding and subtracting calculations involving negative numbers.
This activity combines negative numbers and algebra, which I love. The problem is set as follow:
Given two of each of the ‘weights’ above, different combinations of the weights available allow you to make different totals.
Pupils are asked to make the largest possible number and the smallest possible number then set the challenge to find every integer answer in between.
Not only does this allow the use of integer calculations but gives pupils extra practice writing algebraic expressions.
For example, 2B + D = 2 x (-3) + (-27) = -6 – 27 = -33
Most of my classes love activities where they can compete in group to find the most number of solutions.