📏 Converting Metric Units

What you’ll learn

1. Everything Counts in TensSee that the metric system is built entirely on tens, and understand why that makes changing units easy.Metric length units — kilometre, metre, centimetre, millimetre — each step is exactly ten times bigger or smaller than the next. Because the whole system runs on tens, just like our money and our number system, you never have to memorise messy conversion numbers. Changing units is only ever about moving up or down a tidy ladder of tens.
2. The Length LadderName the four common metric length units in order and state how each relates to the next by tens.The four everyday length units form a ladder: kilometre (km), metre (m), centimetre (cm), millimetre (mm). 1 km = 1000 m, 1 m = 100 cm, and 1 cm = 10 mm, which also makes 1 m = 1000 mm. Picturing them as rungs — big at the top, small at the bottom — is the key mental picture for every conversion that follows.
3. Going Smaller Makes the Number BiggerConvert from a larger unit to a smaller one by multiplying, and explain why the number gets bigger.Changing from a bigger unit to a smaller one means the number of units goes UP, because it takes many small units to fill one big one. To do it, multiply: metres to centimetres is ×100, metres to millimetres is ×1000, kilometres to metres is ×1000. The amount of real length never changes — only the size of the cup you're measuring it in.
4. Going Bigger Makes the Number SmallerConvert from a smaller unit to a larger one by dividing, and explain why the number gets smaller.Changing from a smaller unit to a bigger one means the number goes DOWN, because it takes many small units to make one big one, so you end up with fewer big ones. To do it, divide: centimetres to metres is ÷100, metres to kilometres is ÷1000. It is the exact opposite of the last lesson, and the same test — did the answer move the way you expected? — tells you if you're right.
5. Decimals Slide Along the LadderConvert measurements that include a decimal, such as 3.5 km, by using the same multiply-or-divide rule.Decimals don't change the rules at all: 3.5 km still becomes metres by multiplying by 1000, giving 3500 m. A decimal simply means 'and a bit more' — 3.5 km is 3 whole kilometres plus half of another. Because metric runs on tens, converting a decimal is the same as sliding the decimal point along, which is why 3.5 km, 3500 m, and 350000 cm are all the very same distance.
6. The Very Same Ladder for Weight and LiquidRecognise that mass (grams/kilograms) and capacity (millilitres/litres) convert by the same rule, and practise choosing multiply or divide.The metric idea isn't just for length. Weight uses grams and kilograms (1 kg = 1000 g) and liquids use millilitres and litres (1 L = 1000 mL), and both follow the identical rule: bigger to smaller, multiply; smaller to bigger, divide. Learn the pattern once and it works everywhere, so the real skill is simply deciding which way you're moving on the ladder.

Questions this course answers

Grounded in trusted sources

• SI (metric) prefix values used throughout — kilo = 1000, centi = 1/100, milli = 1/1000, and the relationships 1 km = 1000 m, 1 m = 100 cm, 1 cm = 10 mm, 1 m = 1000 mm: https://en.wikipedia.org/wiki/Metric_prefix
• Metric units of mass and capacity used in the last lesson (1 kg = 1000 g, 1 L = 1000 mL follow the same prefixes): https://en.wikipedia.org/wiki/Metric_prefix

Every Wunder lesson is built from real, reputable sources — never invented.

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