Depth 1 · 35 s
Move the point
Changing between metric units is moving the point, because every step is 10, 100 or 1,000. 2.5 km is 2,500 m (three places right), 150 mm is 15 cm and 210 cm is 2.1 m (left). A smaller unit gives a bigger number.
About this video
Converting between metric units doesn't need hard sums. Each metric unit is 10, 100 or 1,000 times another, so changing units just moves the decimal point. How many metres is 2.5 km? A kilometre is 1,000 metres, and 1,000 has three zeros, so move the point three places to the right: 2,500 m.
Going the other way works too. A pencil is 150 mm long; 10 mm make a centimetre, so move the point one place to the left: 15 cm. A door is 210 cm tall; 100 cm make a metre, so move it two places left: 2.1 m. This animation shows the units as a staircase from kilometres down to millimetres. Going down to a smaller unit, the number gets bigger and the point moves right. Going up to a bigger unit, the number gets smaller and the point moves left.
This video shows depth 1 of Unit conversion.
Learn Unit conversionTranscript
- 0:002.5 kilometres. How many metres is that?
- 0:04A kilometre is 1,000 metres, and 1,000 has three zeros. So move the point three places right: 2,500 metres.
- 0:13To a smaller unit, the number grows. The point goes right.
- 0:17A 150-millimetre pencil: one place left, 15 centimetres.
- 0:21A 210-centimetre door: two places left, 2.1 metres.
- 0:26To a bigger unit, the number shrinks. The point goes left.
- 0:30No hard sums. Just move the point.