Childrens Illustrated Encyclopedia

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386

Numbers

Fractions

sometimes the number 1 has to be

divided into portions. Parts of a

whole number are called fractions.

When We Want to knoW how many things we have, or

measure how large something is, we use numbers. numbers are

symbols that describe an amount. there are only 10 number

symbols: 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9, but they can be put together in many

different ways to make other numbers of any size. Besides counting and

measuring, numbers can also be used to work out time and distances, or to

put things in order. the skill of working with numbers is called arithmetic.

early humans probably used their fingers and thumbs to count. Because we

have 10 digits—eight fingers and two thumbs—we developed a system of

counting that was based on tens. this is called the decimal system,

after the Latin word for 10. numbers are just as important

as words for passing on information. they can be written

down, so that other people can read and use them.

tyPes oF numBer

Whole numbers that stand for

quantities, such as 1, 2, or 3, are

called cardinal numbers. numbers

that put things in order, such as 1st,

2nd, or 3rd, are known as ordinal

numbers. in a fraction, the number

below the line shows how many parts

the whole is divided into; the number

above shows how many of those parts

are being described.

numBers in history

People have invented many different ways of representing

numbers with symbols. the modern decimal system has

now been taken up all over the world, but older systems are

still used in a few places. even the ancient roman system is

used sometimes, especially on clock faces.

A decimal fraction,

10 and 65

hundredths

Pebbles

Cardinal

numbers A fraction, two-thirds

Calculator

using numBers

if you look around, you will see how numbers are

used in everyday life. For example, scoreboards,

speed limits, distances, prices, tV channels, and

the time of day are all shown using numbers. Page

numbers in the index of this book show where

to find the topics that interest you. money is also

divided into units to make it simple to understand.

counting

When people needed to

count higher than 10, they

used objects such as pebbles

to represent multiples of 10.

so, five pebbles and three

fingers stood for the number

53. making calculations with
    pebbles led to the invention
    of the abacus, and later the
    slide rule and calculator.

The Babylonians invented a number system based on 10 about

3,500 years ago, but the symbols took a long time to write down.

The Ancient Roman number system goes back to about 500 bce.

It is an awkward system, but it is still sometimes used today.

In about 200 bce, the Hindus used a number system based on 10.

About 1,400 years ago, they modified it to include zero.

By the 15th century, Hindu-Arabic numbers had replaced Roman

numerals as the most popular number system.

Today, most countries use a modern version of the Hindu-Arabic

number system, because it makes calculations easy.

alphabets

computers

mathematics

science

Find out more

Cricket scoreboard

Using fingers

Ruler

US_386_Numbers.indd 386 22/01/16 4:45 pm