Reading that a fence stays the same length is one thing. Bending the garden yourself and watching the number refuse to move is another. Nothing here is marked — just pull it around.
Set how many of the eight parts are black, then spin. The wheel does not care how the parts are arranged — only how many there are.
Drag the snail along the ruler. Two numbers keep changing. One number refuses to.
head − tail never changes while you drag. That is why you work out the length first — then the new head is just new tail + length.Same jug. Same water. Change the number written at the top and the answer changes completely.
Three pieces, one dotted outline. The slanted edges only fit one way round.
Push the step in and out. Six side lengths change as you do it. Watch the fence.