About this game

Some farm animals are waiting by a river, and there's a gap between the two stone banks. The class picks planks from the pile, such as 2, 1 and ½, and lays them across. When the planks fill the gap, an animal walks over.

If the bridge is too short, the animal walks to the end, wobbles, and falls in. The board says by how much it was short. If it's too long, the last plank won't drop in and sticks out over the far bank. The sum is written at the top as the planks go down: 2½ + 2 + 1 = 5½.

A measuring tape under the gap marks every half, quarter or sixth. Turn it off when the class is ready to work out the lengths without it.

Two games

• Three ways across. Three animals each need a different bridge. The same planks in another order don't count. At the end the game says how many ways there are in all.
• Fewest planks. The pile only has a few of each plank. The class tries to cross on as few as possible. Taking the longest plank each time often gets stuck, so there's something to talk about.

Good for

• Number bonds and adding several numbers
• Adding fractions with the same or related denominators
• Equivalent fractions: ½ is two quarters, ⅔ is four sixths
• Mixed numbers, and finding the difference