Chapter 7 Decimals Worksheet - New Century Maths Page 32
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387 The answers to the following are whole numbers but, for particular reasons, some need to
be rounded up and some need to be rounded down. Find the answers.
a A box of chocolates with 33 chocolates is shared among a family of five people.
How many chocolates does each person receive?
b A new bathroom requires 32 square metres of tiles. The tiles come in boxes
containing 1.5 square metres. How many boxes are needed to tile the bathroom?
c A team of four golfers wins 27 new golf balls in a competition. How many does each
person receive?
d Some timber comes in 1.8 m lengths. How many lengths are needed to build a chicken
house needing 23 m of timber?
e Each blouse requires 1.3 m of material. How many blouses can be made from a 5 m
length of material.
8 Give a reason for:
a rounding up
b rounding down.
SkillBuilder
Working mathematically
1-09
Rounding
Questioning and reflecting: Rounding prices
money
Since the use of 1c coins and 2c coins stopped in 1990, prices have been rounded to
the nearest 5 cents. Find out:
a when amounts are rounded
b how amounts are rounded (check the major stores in your area)
c what happens with bills such as electricity, phone, etc.
d who decides how the rounding will work.
Just for the record
The salami technique
When banks started using computers to keep track of customers’ accounts, they left
themselves open to a new type of crime: computer theft. One such crime employs the
salami technique, where computer hackers steal a cent or a fraction of a cent from
many bank accounts. They round down the decimal amount of an account balance (for
example $234.6523 would become $234.65) and the stolen fraction of a cent
($0.0023) is deposited into the hacker’s account, with no one noticing it missing. When
this is done to thousands of bank customers over a number of years, a considerable
amount of money can be accumulated.
If the salami technique is applied to $1723.35631, $456.3277, $6701.2315 and
$488.29891, how much will the computer criminal have in his or her account?
Why do you think this type of crime is difficult to detect?
Why do you think it is called the ‘salami technique’?
229
DECIMALS
CHAPTER 7
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