Numbers written in places

Brief

This lesson asks you to read, build and break apart whole numbers up to 200 and to say how numbers are used in everyday life. The museum offers one account of how numbers are written in places, with units, tens and hundreds; the objects, the drawings and all the practice your class brings. Adding and subtracting with objects, diagrams and equations is not covered here. ¹

How can one number be taken apart?

Pick a number between 100 and 200. The expectations ask you to compose and decompose it with tools: try bundles of ten, a hundred chart or place-value blocks, and compare the ways you found.

Go deeper

The record on algorism has a picture for young readers. About twelve hundred years ago a scholar in Baghdad named al-Khwarizmi wrote a book teaching people to calculate with nine numerals that came from India, together with zero ² ³. With these numerals you only need to move a digit to change its value: a one can mean one, ten or a hundred! ² ³

Think about it

A one can mean one, ten or a hundred, depending on where it stands. Why does it matter that you put each digit in the right place when you write a number?

Into the museum

Algorism: the whole story of the nine numerals and the zero.
al-Khwarizmi: the scholar who wrote the book, and where he worked.
al-Khwarizmi's Book of Arithmetic: the book, and the words that came from his name.

Try this

Read the record on algorism. Choose a number under 200, write it in its places, and say how many hundreds, tens and ones it has.