Before the invention of written numbers，people used many different ways to count things.At （1）

first

first

（one），people used their fingers，and even their toes.However，they could only count small numbers （2）

in

in

this way.
    After that，they began to make small （3）

marks

marks

（mark） on sticks and bones.This helped them count much （4）

bigger

bigger

（big） numbers.They used them to count things like the days of （5）

a

a

month，the amount of food and the number of animals they had.
    Then people began to use tokens made from clay （6）

or

or

small stones.This helped （7）

them

them

（they） count even bigger numbers.They often put the tokens on pieces of string so that they could carry them around （8）

easily

easily

（easy）.This developed into tools like the abacus.
    Finally，people （9）

began

began

（begin） to develop systems of written marks to show different numbers，and this led to the Hindu-Arabic system （0-9）.We are still （10）

using

using

（use） this system today.