Page 20 - Math Smart - 7

CHAPTER 1.3

In this chapter
Tests of Divisibility
Pupils should be able to:
• use the tests of
divisibility for 2, 3, 4, 5, The bar code on items you buy is like a fingerprint of the item. Each
different item has its own unique barcode. The first six digits in a
6, 8, 9, 10 and 100
12-digit barcode number are the manufacturer identification number.
The next five digits are the item number. The last digit is called the
^ RECALL check digit. This digit can be used to check whether the number has

been scanned correctly.
Q Even numbers end
with a digit which
is . All even
numbers can be
• Think and Share
divided by .
Q Odd numbers end Let's check whether the bar code 639382000393
with a digit which is
is correct:
. Odd numbers
O Cross out the last digit: 63938200039^
cannot be divided by
© Add all the digits in odd positions
(1«, 3rd^ 5ih^ j jp, code; 39382 00039
6 + 9 + 8 + 0 + 0 + 9 = 32
© Multiply the answer by 3.
32 X 3 = 96
O Add all the digits in even positions (2"^, 4'^ 6'^ ...) in the code:

The calculation of the 3 + 3 + 2 + 0 + 3 = 11
check digit in a bar code © Add the answer in Step 4 to the answer in Step 3: 96 + 11 = 107
requires you to know
O Create the check digit by determining what number should be
whether one number
added to the number in step 4 to make the number divisible by 10.
is exactly divisible by
107 + 3 = 110
another number. The
tests of divisibility can be The check digit is therefore 3.
used to help you quickly The complete bar code number is therefore: 639382000393
establish that, especially
when working with
large numbers such as a
12-digit barcode.

UNITl Factors, Multiples and Primes