Aim of learning: addition and subtraction, using and recording trial and error methods, relationships between numbers
How many players: 2+
You will need: A3 paper and pencils
Turn the paper to portrait- along the top draw a numberline and label numbers from 1 to 20 along it. One person is adding and the other is subtracting- decide who will do what with your partner.
The first person chooses 2 numbers to add together which have a total on the numberline. 4+16 =20. The first person crosses out the first 2 numbers used (4 and 16) and circles the answer. (They record below what they have done.)
The second person starts with the circled answer and takes away another number from it to make a new total: 20 – 9 = 11. The second person crosses out the 20 and the 9 and circles 11.
Any number that is circled is always the starting point for the next person’s go. The first 2 numbers are always crossed out and cannot be used again. The second person also records what they have done. As the game progresses it becomes more difficult because there are less numbers to use.
There are different ways to play:
Against each other- with the person who cannot complete a sum losing (or the person with the most sums recorded winning).
As partners co-operating -to see if they can strike out as many different numbers as they can. What is the least amount of numbers that you can be left with? Is it possible to strike them all out?
There are lots of variations like: changing how many numbers are on the numberline- how about 21 or 25? Does that affect how many numbers can be struck out?
Using all 4 operations is interesting too