The dimensions of a large room are double the dimensions of a small room.
both rooms are rectangular prisms. the volume of the small room is 10 cubic
metres.
what is the volume of the large room?

The volume would be 80 cubic metres. Think about the three different dimensions for the small room as x,y and z. Therefore the volume is x*y*z= xyz. Now for the bigger room, the dimensions would be 2x,2y and 2z. Therefore, its volume would be 2x*2y*2z= 8xyz. Since xyz (volume of the smaller room)= 10 cubic metres, the bigger room's volume will be 8*10= 80 cubic metres.