Lesson Guide
Explanation
You can measure the distance to the next town in metres. It would come out at something like 42000 metres, which is correct and completely useless — nobody can picture 42000 of anything. So for long distances we use a bigger unit: the kilometre, which is 1000 metres. The same distance becomes 42 kilometres, a number you can actually hold in your head. Kilo means a thousand, which is the same kilo you already know from kilogram.
Your Turn
How many metres in 3 kilometres? Check: 3000 metres.
Watch Out
Kilo always means a thousand. A kilometre is a thousand metres, never a hundred.
Explanation
A kilometre is easier to remember if you attach it to something real. Most people walk one in about twelve minutes. It is two and a half laps of a 400 metre running track, or twenty lengths of a 50 metre pool. In a car on the highway you cover one in well under a minute. If you ever get the chance, walk a measured kilometre and time it — after that you will always have a feel for the distance, and estimating gets much easier.
Your Turn
Roughly how long would it take you to walk 3 kilometres? Check: about 36 minutes, at twelve minutes each.
Watch Out
A kilometre is a long way to walk and a short way to drive. The unit is the same; what changes is how you travel.
Explanation
Kilometres to metres, multiply by 1000. Metres to kilometres, divide by 1000. So 5 km is 5000 m, and 7500 m is 7.5 km. There is a check that catches almost every mistake: if you move to a smaller unit the number must get bigger, because it takes more small things to cover the same distance. Turning 5 km into 0.005 m should feel instantly wrong — you went to a smaller unit and the number shrank.
Your Turn
Convert 2 km to metres, and 4500 m to kilometres. Check: 2000 m, and 4.5 km.
Watch Out
Ask yourself whether the answer should be bigger or smaller BEFORE you calculate. Then check that it is.
Explanation
Distances rarely land on whole kilometres, so you meet decimals: 0.5 km is half a kilometre, which is 500 metres. A quarter, 0.25 km, is 250 metres. It works exactly like money — a kilometre splits into 1000 metres the way a dollar splits into 100 cents, and the decimal point does the same job. And 1.5 km means a whole kilometre plus another half, so 1500 metres in total.
Your Turn
How many metres in 2.5 km, and in 0.75 km? Check: 2500 m and 750 m.
Watch Out
0.5 km is 500 m, not 50 m. Multiplying by 1000 moves the digits three columns, not one.
Explanation
You now have four units for length, and the skill is picking the right one. The test is simple: choose the unit that keeps the number small and sensible. A pencil in millimetres gives 180, which is clumsy — 18 centimetres is better. A road trip in metres gives 350,000, which is absurd — 350 kilometres is better. Nobody would say a pencil is 0.00018 kilometres, even though it is perfectly true. Right unit, comfortable number.
Your Turn
Which unit would you use for: your height, a bee, the drive to the beach? Check: centimetres, millimetres, kilometres.
Watch Out
Every conversion is technically correct, but the wrong unit makes a number nobody can use. Pick for the reader.
📌 Key Points — this lesson in a nutshell
- 1 km = 1000 m. "Kilo" means a thousand.
- km → m: × 1000. m → km: ÷ 1000.
- Smaller unit → bigger number. Use that to check every conversion.
- A kilometre is about a 12 minute walk, or 2 and a half laps of a track.
- Pick the unit that keeps the number small and sensible.
Step 1: Introduction
Step 1 of 5
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