149
- = 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 the previous chapter we saw how to divide by large numbers
using factors. Th is principle is central to all long division, including
standard long division commonly taught in schools.
Division by factors worked well for division by numbers such as 36
(6 × 6), 27 (3 × 9), and any other number that can be easily reduced
to factors. But what about division by numbers such as 29, 31 or
37, that can’t be reduced to factors? Th ese numbers are called prime
numbers; the only factors of a prime number are 1 and the number
itself.
Let me explain how our method works in these cases.
If we want to divide a number like 12,345 by 29, this is how we do
it. We can’t use our long division by factors method because 29 is a
prime number. It can’t be broken up into factors, so we use standard
long division.
CChapter 15hapter 15
STANDARD STANDARD LONG L ONG
DDIVISION MADE EASYIVISION MADE EASY
- = x 0 1 2 3 4 5 6 7 8 9 ( ) % < > + - = x 0 1 2 3 4 5 6 7 8 9 ( )