# Video: Identifying 3D Shapes That Stack, Slide, or Roll

Think about shapes that can roll, stack, and slide. One of these shapes can roll and slide. Which one? One of these shapes can slide and stack. Which one?

03:06

### Video Transcript

Think about shapes that can roll, stack, and slide. One of these shapes can roll and slide. Which one? One of these shapes can slide and stack. Which one?

This question encourages us to think about whether shapes can roll, stack, and slide. And you know some shapes can do more than one of these things. The first part of the question asks us to find one of the shapes that can both roll and slide. And we’re given two shapes to look at. The green shape is a cube, and the red shape is a cone.

Now, which of these two shapes can do two things, roll and also slide? Now, for a 3D shape to slide along if we push it, it’s going to need to have a flat surface. But we can see that both of our shapes have at least one flat surface. So they’re both going to be able to slide. But for a 3D shape to roll, it’s going to need to turn over and over again. And for this, it’s going to need a curved surface. Which of our two shapes has a curved surface? It’s the cone. It has a flat surface and a curved surface. And if we stand it upon its flat surface, it will slide. But if we turn it onto its curved surface on the side, we can make it roll too.

In the second part of the question, we’re shown two more 3D shapes. The first shape is not a cuboid, but it might remind us of one. Looks a little bit like a cuboid, doesn’t it? And we know the name of our second shape. It’s a pyramid. And we’re told that one of these shapes can slide and also stack. Is it our unusual yellow shape or our purple pyramid?

Well, we already know that to slide a shape, it needs a flat surface. And both of these shapes do have a flat surface. If we put them on a tabletop and push them, they’d both slide. But which one could we stack on top of each other? Well, for us to be able to stack a 3D shape, it needs to have flat surfaces at either end. Our pyramid might have a flat surface at one end, but at the other end there’s a point. Can you imagine trying to balance one pyramid on top of another? We can’t stack pyramids.

But if we look carefully at our first shape, we can see that it does have flat surfaces opposite each other. Because it’s such an unusual shape, it might make a bit of a wonky tower, but we can still stack it. The shape that can both roll and slide is the red cone, and the shape that can both slide and also stack is the yellow shape.