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Primary General Studies: Weather, Water and Energy Paper 3 (rainfall harvesting and electricity use)
Primary General Studies: Weather, Water and Energy Paper 3 (rainfall harvesting and electricity use)
Paper 3 links rainfall, water use and electricity through one conversion line: change millimetres or watts into litres or units first, then multiply by days or area.
Quick answer One litre per square metre; 50 billion litres; 880 litres; six units; 26,400 litres; 1.5 units; 1,460 litres; 96,000 litres; 1.65 million cubic metres; one millimetre is one litre.
01 Paper details (check answers afterwards)
| Item | Detail |
|---|---|
| Questions | 10 questions |
| Suggested time | 25 minutes |
| Difficulty mix | Foundation 4 · Intermediate 3 · Challenge 2 · Error redo 1 |
| Chapter | Chapter: Primary General Studies: Hong Kong Life and Environment |
| Level | P6 |
02 Questions (10 items)
- FoundationHow many litres does one millimetre of rain deliver to one square metre?
- FoundationA reservoir holds 50 million cubic metres. How many litres is that?
- FoundationEach person uses 220 litres a day. What does a family of four use in litres and cubic metres?
- FoundationAn air conditioner draws 1,500 W. How many units does it use in four hours?
- IntermediateA family of four uses 880 litres a day. What is the 30-day total in litres and cubic metres?
- IntermediateA 300 W panel gets five effective sun hours a day. How many units does it make daily and in thirty days?
- IntermediateFour people each drink two 500 mL bottles a day. How many litres is that in a year?
- ChallengeA roof of 40 square metres gets 2,400 mm of rain a year. If all is collected, how many litres and cubic metres is that?
- ChallengeAbout 7.5 million people each use 220 litres a day. What is the daily total in litres and cubic metres?
- Error redoError repair: a pupil says one millimetre of rain is ten litres per square metre. What is correct?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | one litre | One millimetre over one square metre is one litre, so depth converts directly into volume. |
| 2 | 50 billion litres | One cubic metre is 1,000 litres, so fifty million times one thousand is fifty billion litres. |
| 3 | 880 litres, that is 0.88 cubic metres | Four times 220 is 880 litres, and dividing by one thousand gives 0.88 cubic metres. |
| 4 | six units | One thousand five hundred times four divided by one thousand is six units. |
| 5 | 26,400 litres, that is 26.4 cubic metres | Eight hundred and eighty times thirty is 26,400 litres, and dividing by one thousand gives 26.4 cubic metres. |
| 6 | 1.5 units a day, 45 units in thirty days | Three hundred times five divided by one thousand is 1.5 units, and thirty days give 45 units. |
| 7 | 1,460 litres | Four times two times five hundred millilitres is 4,000 mL, that is 4 litres, and a year gives 1,460 litres. |
| 8 | 96,000 litres, that is 96 cubic metres | Each square metre collects 2,400 litres, so times forty is 96,000 litres, and dividing by one thousand gives 96 cubic metres. |
| 9 | 1.65 x 10^9 litres, that is 1.65 million cubic metres | Seven point five million times 220 is 1.65 x 10^9 litres, and dividing by one thousand gives 1.65 million cubic metres. |
| 10 | one litre per square metre | A millimetre of water over a square metre is a slab one millimetre deep, a thousandth of a cubic metre, that is one litre. |
04 What to do after marking
- After marking, redo only the wrong items and write down which step went wrong (formula, unit, or misread number).
- Repeat the same item two days later; move to the next paper only when both attempts are correct.
- Parents only need the answer and note columns; there is no need to explain every item.
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