Finding water level from volume and base area

Tanks A and B are rectangular. Tank A is 25 centimetres long, 16 centimetres wide and 20 centimetres high. The water in Tank A is 12 centimetres deep. Tank B is 40 centimetres long and 15 centimetres wide, and it is empty. All the water in Tank A is poured into Tank B. Find the height of the water level in Tank B. Try it first. Pause if you like. Let us look at these same two tanks in depth. We need the water volume and the base area it will stand on in Tank B. Volume equals base area times height. Start with Tank A. Its base is twenty-five centimetres long. Its breadth is sixteen centimetres. Multiply these two lengths to find the base area. The base area is four hundred square centimetres. Twenty centimetres measures the whole tank. The water only reaches twelve centimetres. Use this water depth. Multiply four hundred square centimetres by twelve centimetres. Square centimetres times centimetres gives cubic centimetres. The volume of water in A is four thousand, eight hundred cubic centimetres. Now find the receiving base area. Tank B is forty centimetres long. Its breadth is fifteen centimetres. Multiply forty centimetres by fifteen centimetres. The base area of B is six hundred square centimetres. Tank A has a base area of four hundred square centimetres. Tank B has a wider base area of six hundred square centimetres. Watch all the water move across and spread over this wider base. Nothing was added or lost. It is still four thousand, eight hundred cubic centimetres. The old level is marked in Tank A. On the wider base, the water height is lower. To find that height, divide the water volume by the base area of Tank B. Four thousand, eight hundred cubic centimetres divided by six hundred square centimetres. Cubic centimetres divided by square centimetres leaves centimetres. The water level in Tank B is eight centimetres. Use Tank B’s base area, because that is where the water stands now. Same water. A wider base. A lower level.