Why convert units first?

Mixing metres and kilometres shifts the answer by a thousand times, so converting first keeps the order of magnitude right.

How is solid waste estimated?

Multiply the population by the waste per person per day, then change kilograms to tonnes by dividing by one thousand.

Primary General Studies: Hong Kong Life and Environment Paper 2 (area, time zones and waste)

2026-11-03

P · r

Paper 2 focuses on unit conversion and two-step problems: convert to one unit first, then multiply or divide.

Quick answer　69 square kilometres; 63 hours; yellow; 3,500 m; 2 pm; 18 degrees Celsius; six cups; 11,250 tonnes; 60 items; one litre is 1,000 millilitres.

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)

FoundationLantau is about 147 square kilometres and Hong Kong Island about 78. What is the difference?
FoundationA doctor advises nine hours of sleep a day. How many hours is that in a week?
FoundationIn the three-colour scheme in Hong Kong, which bin takes metal cans?
FoundationOne kilometre is 1,000 m. A harbourfront stretch is 3.5 km long. How many metres is that?
IntermediateHong Kong time is one hour behind Tokyo. When it is 3 pm in Tokyo, what time is it in Hong Kong?
IntermediateWater freezes at 0 degrees Celsius. By how many degrees must 18 degree water cool before ice forms?
IntermediateA child should drink 1.5 litres of water a day from 250 mL cups. How many cups is that?
ChallengeHong Kong has about 7.5 million people who each throw away 1.5 kg a day. What mass is discarded daily, in kilograms and tonnes?
ChallengeThirty pupils each collect twelve plastic bottles. If six bottles make one garment, how many garments is that?
Error redoError repair: a pupil says one litre is 100 millilitres. What is the correct conversion?

03　Answers and one-line notes

#	Answer	One-line note
1	69 square kilometres	One hundred and forty-seven minus seventy-eight is 69.
2	63 hours	Nine times seven is 63.
3	the yellow bin	Yellow takes metal cans, blue takes paper and brown takes plastic bottles.
4	3,500 m	Three point five times one thousand is 3,500 m.
5	2 pm (14:00)	Three in the afternoon minus one hour is 14:00, or 2 pm.
6	18 degrees Celsius	Eighteen minus zero is eighteen degrees.
7	six cups	One and a half litres is 1,500 mL, and 1,500 divided by 250 is 6.
8	11.25 million kg, that is 11,250 tonnes	Seven point five million times 1.5 is 11.25 million kg, and dividing by one thousand gives 11,250 tonnes.
9	60 garments	Thirty times twelve is 360 bottles, and 360 divided by six is 60 garments.
10	one litre is 1,000 millilitres	A litre is a thousand times a millilitre, so one litre is 1,000 mL and not 100 mL.

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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