The idea in brief. Water that is poured out keeps its VOLUME and changes its SHAPE, because the floor under it changes. So a known volume standing at a known depth gives the floor it is standing on, and if the tank is cubical, that floor is a square and its side is the square root of its area. In the lesson. The same poured water has a different depth in B because it stands on a different square base.
Lesson video, with the working
Pouring water between two containers
3 min 14 s
The film teaches 1 question. The question shows first; its working is written as the film explains it.
Tank A and Tank B are cubes. Tank A has an edge of 30 cm and is full of water. Tank B is empty. 1/10 of the water in Tank A is poured into Tank B. The water heights in A and B are then in the ratio 9 : 4. (a) Find the volume poured. (b) Find the length of one edge of Tank B.
(a) The volume of water poured into Tank B is 2700 cm³.
(b) One edge of Tank B is 15 cm.
Ans: 2700 cm³15 cm
How to solve it
Find the water poured: one tenth of 30 times 30 times 30 is two thousand, seven hundred cubic centimetres.
Find the height left in Tank A: 1 minus one tenth, times 30, is 27 centimetres.
Use the ratio 9 to 4: 9 units are 27 centimetres, so 1 unit is 3, and Tank B's 4 units are 12 centimetres.
Find Tank B's base area: two thousand, seven hundred divided by 12 is 225 square centimetres.
A cube's floor is a square, so the edge is the square root of 225, which is 15 centimetres.
The same water, a smaller floor, a deeper level.
Practice questions with worked solutions
Question 1 is free to try. The other 10 open in the free trial, each with its full working.
Question 1 of 11 · Basic · free to tryAll the syrup in a jug was poured into one large bottle. It was 180 ml short…All the syrup in a jug was…
All the syrup in a jug was poured into one large bottle. It was 180 ml short of filling the large bottle to the top. The same jug of syrup would instead have filled one small bottle to the top and left 220 ml over. A small bottle holds 500 ml. Find the capacity of the large bottle.
How do you solve pouring water between tanks questions in P6?
Water is poured from one container into another, and the question asks for a new depth, a base, or how the containers compare.
What your child learns here
Water is poured from one container into another, and the question asks for a new depth, a base, or how the containers compare. The water's volume does not change when it moves, only its shape. These exam-style questions apply the Primary 6 outcomes on finding a dimension or height from a volume.
Find the volume of water in the first container, then divide it by the second container's base area.
Find the amount poured out from the drop in level times the base area.
Treat a ratio of depths as a ratio of depths, and recover the volume through the base area.
Compare containers holding the same water: the one it fills a smaller fraction of is the bigger one.
When a solid block is placed in water, count only the part of the block below the surface.
Does the answer make sense?
Pouring changes the water's shape, never its volume, so when the same water moves to a tank with a smaller base its level must rise, and to a larger base it must fall. A block your child lowers into the water can only push the level up, never down.
How to practise these questions
The Intermediate questions train moving water between containers by keeping the volume the same while base areas change, including blocks placed in water and containers turned over. Challenge questions spread one depth over two bases, or compare capacities using what fraction of each is filled. When pouring between containers gets muddled, read the written step-by-step solution together.
Questions parents ask
How do you solve questions where water is poured from one tank to another? Find the volume of water that moves, using the first tank's base area and the change in depth. Then divide that volume by the second tank's base area to get the new depth.
Does the volume of water change when it is poured? No. The amount of water stays the same; only its shape changes. A smaller base makes it stand deeper, and a larger base makes it shallower.
Which syllabus outcome do pouring questions use? They use the Primary 6 outcome on finding the height of a cuboid given its volume and base area, together with the Primary 5 outcome on the volume of liquid in a rectangular tank.
