Lesson 2 of 4

Converting units.

About 25 minutes · 6 practice questions

Read the full article: Units of measurement

Converting a unit is a fixed ratio: kilometres to metres, hours to minutes, metres per second to kilometres per hour, units of area, and the scale of a map.

Step 1 of 6 · Kilometres to metres

Step 1 of 6

Kilometres to metres

One kilometre is 1000 m: kilo means a thousand. Converting units is a fixed ratio, $1 : 1000$ ⁠, so the same two lines work: kilometres on top and metres below. Going to a smaller unit makes the number bigger, because every big unit splits into many small ones.

Marker is locked at 2.5 km. Answer, then drag Look inside to check.

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Step 2 of 6

Centimetres to metres

One metre is 100 cm: centi means a hundredth. Going to a bigger unit makes the number smaller, because it takes fewer metres than centimetres to measure the same length.

Move Marker until the bottom line reaches the ring at 350 cm, then press Check.

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Step 3 of 6

Hours and minutes

An hour has 60 min, not $100$ ⁠. So in a number like 1.25 h the digits after the point are a part of an hour, not the number of minutes.

Marker is locked at 1.25 h. Answer how many minutes that is, then drag Look inside to check.

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Step 4 of 6

A speed in two units

A speed of 1 m/s is one metre every second. An hour has $3600$ ⁠ seconds, so that is 3600 m an hour, or 3.6 km/h. Here two units change at once, and what is left in the end is one multiplication, by $3.6$ ⁠.

A person walks at 1.5 m/s. Answer, then drag Look inside to check.

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Step 5 of 6

Units of area

The square on the board is 10 cm by 10 cm, and inside it are small squares of one centimetre by one centimetre: $10 \times 10 = 100$ ⁠ square centimetres. The side grew $10$ ⁠ times, and the area grew $10 \times 10 = 100$ ⁠ times.

What happens in a square metre, a square whose side is 100 cm?

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Step 6 of 6

The scale of a map

On a map at a scale of 1:50,000, every centimetre on the map is 50,000 cm on the ground, that is 500 m, or 0.5 km. That too is a fixed ratio: centimetres on the map on top, kilometres on the ground below.

Marker is locked at 3 cm. Answer, then drag Look inside to check.

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Interactive scene

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Each step sets up the Scene for you, and a control marked “fixed” stays put for that step.

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