43
- = x 0 1 2 3 4 5 6 7 8 9 ( ) % < > + - = x 0 1 2 3 4 5 6 7 8 9 ( )
% < > + - = x 0 1 2 3 4 5 6 7 8 9 ( ) % < > + - = x 0 1 2 3 4 5 6 7 8 9
( ) % < > + - = x 0 1 2 3 4 5 6 7 8 9 ( ) % < > + - = x 0 1 2 3 4 5 6 7 8
9 ( ) % < > + - = x 0 1 2 3 4 5 6 7 8 9 ( ) % < > + - = x 0 1 2 3 4 5 6 7
8 9 ( ) % < > + - = x 0 1 2 3 4 5 6 7 8 9 ( ) % < > + - = x 0 1 2 3 4 5 6
7 8 9 ( ) % < > + - = x 0 1 2 3 4 5 6 7 8 9 ( ) % < > + - = x 0 1 2 3 4 5
6 7 8 9 ( ) % < > + - = x 0 1 2 3 4 5 6 7 8 9 ( ) % < > + - = x 0 1 2 3
In Chapters 1 to 4 you learned how to multiply numbers using
an easy method that makes multiplication fun. It is easy to use
when the numbers are near 10 or 100. But what about multiplying
numbers that are around 30 or 60? Can we still use this method?
We certainly can.
We chose reference numbers of 10 and 100 because it is easy to
multiply by 10 and 100. Th e method will work just as well with
other reference numbers, but we must choose numbers that are easy
to multiply by.
MULTIPLICATION BY FACTORS
It is easy to multiply by 20, because 20 is 2 times 10. It is easy
to multiply by 10 and it is easy to multiply by 2. Th is is called
multiplication by factors, because 10 and 2 are factors of 20 (20 =
10 × 2). So, to multiply any number by 20, you multiply it by 2 and
CChapter 6hapter 6
MMULTIPLICATION ULTIPLICATION
UUSING SING ANY A NY
RREFERENCE NUMBEREFERENCE NUMBER
- = x 0 1 2 3 4 5 6 7 8 9 ( ) % < > + - = x 0 1 2 3 4 5 6 7 8 9 ( )