Large Numbers Roll Over

Key Ideas

Check that the students understand that 10 one thousands equals one ten thousand not,  as is commonly thought, one million.

Using Materials

Problem: “Work out $9,993 + $9.”

Record $9,993 + $9 on the board or modelling book. With play money, model $9,993  and $9. Discuss why the 12 single dollars must be swapped for a ten-dollar note and  two single dollar notes. Discuss why nine tens plus the extra ten-dollar note makes 10  tens, which must be swapped for a one-hundred-dollar note. Continue these swaps  until there is a single ten-thousand-dollar note and two single dollars. Record the  answer of $10,002 on the board or modelling book.

Problem: “Work out $10,003 – $4.”

Record $10,003 – $4 on the board or modelling book. Using play money, break the $10,000 down to 10 one-thousand-dollar notes, break the one-thousand-dollar note down to 10 one-hundred-dollar notes, and so on until there are 13 single dollars.

Record the answer of $9,999 on the board or modelling book.Examples: Word stories and recording for: $9,988 + $19   $6 + $52,994,   $116 + $9,884   $40,003 – $7   $20,000 – $100   $999 + $1,004   $1,001– $45   $50,003 – $5 ...

Using Number Properties

Examples: Word stories and recording for: 8 992 + 9   6 + 12 996   16 + 6 684 44 503 – 7   18 900 + 102   99 + 12 099   50 + 6 150   102 003 – 5 ...