## Test Yourself – an explanation of the answers

If you did not understand the answers to the questions in our test or you got a few wrong, this page might be helpful to help you understand what the right answers were and why.

Let us look at each question in turn.

1. How many centimetres in 1 metre?

The correct answer is 100.

1 metre = 100 centimetres. The prefix centi is what tells you that the answer is 100, as centi means one hundredth part of something. Think of the US currency, where they have 100 cents in 1 dollar. It is the same with metric, 100 centimetres = 1 metre.
Bonus fact:
1 metre is approximately the height of door handles on doors in the home.

2. How many cubic centimetres in 1 litre?

The correct answer is 1000.

1 cubic centimetre is the same as 1 millilitre. 1000 millilitres = 1 litre. The prefix milli means one thousandth part of something, not to be confused with the word million. The milli comes from the Latin word mille which means one thousand.
Bonus fact:
Engine capacities are sometimes given as cc, sometimes as litres. The cc means cubic centimetres, and if your engine capacity is 1.4 litres it can also be described as 1400 cc.

3. Which is longer, 1 km or 1 mile?

The correct answer is 1 mile.

This is because 1 mile is the same as 1.6 km, so the mile is longer. When UK drivers go abroad and see km and km/h signs in foreign countries, remember that km are shorter. If the UK used km on the roads then thinking about whether miles or kilometres are longer will no longer be necessary.
Bonus fact:
the word mile actually comes the Latin mille, meaning 1000, as the original Roman mile was defined as 1000 paces of a Roman legion (approx 1.48 km).

4. If a place is 4000 metres away, how many kilometres is this?

The correct answer is 4 km.

Remember that 1 kilometre is 1000 metres, the prefix kilo means 1000 of something. So for every 1000 metres of distance, it is 1 km. E.g. 12,345 metres = 12.345 km.
Bonus fact:
Kilo comes from the Greek khiloi and means 1000.

5. The edge of space is 100 km above the Earth's surface, but how much is this in metres?

The correct answer is 100,000 metres.

As stated in question 4, 1 kilometre = 1000 metres. Therefore to convert 100 km into metres, just multiply by 1000 to get 100,000 km. Another way to look at it is this: the prefix kilo means 1000, which has 3 noughts. So remove the kilo prefix and add 3 noughts instead to the end of the number. If there is a decimal point in the number, e.g. 12.3 km, then look at how many numbers after the decimal point, subtract that from 3. In this case take 1 from 3, leaving 2, so write down the numbers 123 and add 2 noughts to get 12300, i.e. 12,300 metres. If there are more than 3 numbers after the decimal point, then write down the numbers before the decimal point and the first 3 after it, then put in the decimal point, and then add the other numbers. E.g. 4.8765 km = 4876.5 metres.
Bonus fact:
In October 2004 the X-prize was won by a privately sponsored rocket ship that reached the edge of space at 100 km altitude.

6. How many micrograms in 1 gram?

The correct answer is 1,000,000, i.e. one million.

The prefix micro denotes one millionth part of something. It comes from the Greek mikros, meaning small. The symbol for micro is the Greek letter mju, written as µ. 1 gram = 1,000,000 µg. Micrograms are often used in medicines for denoting how much of the particular medicine is in each tablet, such as 200 micrograms, sometimes written as mcg instead of µg.
Bonus fact:
In between micrograms and grams we also have milligrams, and 1000 µg = 1 milligram (mg). 1000 mg = 1 gram.

7. How many millimetres in 2 centimetres?

The correct answer is 20 mm.

There are 10 millimetres in 1 centimetre. We already saw earlier that milli means one thousandth part of something, and that centi means one hundredth part. The difference in scale of 100 and 1000 is 10, i.e. 100 × 10 = 1000. There are 1000 millimetres in 1 metre. 1 mm is one thousandth of a metre. 1 cm is one hundredth of a metre. So 1 cm is also 10 one-thousandths of a metre.
Bonus fact:
Although millimetres seem very small, there are many much smaller units of length in metric, going all the way down to the atomic level with attometres.

8. At what temperature does water boil?

The correct answer is 100 °C.

The Celsius scale (sometimes referred to by its older name, Centigrade) is based on a system where water boils at 100 degrees and freezes at 0 degrees. This makes it very easy to use, as any water that reaches 100 °C will boil, and above that temperature it will be steam or vapour.
Bonus fact:
Since there are one hundred graduations between these two reference points, the original term for this system was centigrade (meaning 100 parts). But it was changed to Celsius to be named after the man who invented the system, Anders Celsius.

9. Which of these is the most typical weight of a newborn baby?

The correct answer is 3.4 kg.

Although weights of babies vary quite a bit, the average is around 3.4 kilograms. The other answers in the list include litres and centimetres, which measure volume and length respectively, not weight. 3.4 grams would be much too lightweight, even for the smallest monkey in the world, the pygmy marmosett, which weighs 10 grams at birth and grows to 150 grams. 3.4 milligrams is even smaller and is more likely to be seen in measuring medicinal content in tablets than any babies.
Bonus fact:
The weight of the newborn's body is only about 5% of its expected adult weight, i.e. a baby will grow to 20 times its birthweight by adulthood.

10. What would be the most suitable unit of these to measure the height of a person?

The correct answer in centimetres.

From the other choices, kilograms measures weight, kilometres measures distance, degrees Celsius measures temperature, and metres per second measures velocity (speed). Typical adult heights range from 150 cm to 180 cm, but this can vary. Remember that 100 cm = 1 metre, so we could say a person's height is 175 cm or 1.75 m.
Bonus fact:
The world's tallest man recorded in history was Robert Wadlow who grew to be 272 cm tall. That's about 1 metre taller than your average man today.

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Page last updated on 29 April, 2006

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