Page 109 - Cambridge+Checkpoint+Mathematics+Coursebook+9

11.4 Practical examples

6 A man invests $4500 in a bank. The bank pays 8% interest.
a Work out the interest, in dollars.
b Work out the total.

7 A woman deposited $560 in a bank.
a The bank decided to give all its customers 4.5% interest. Calculate how much she received
in interest.
b The next year she had $720 in the bank and received $27.36 interest. What was the percentage
interest rate?
8 Barry lends Cara $6400.
Cara agrees to give Barry 5.5% interest every year for four years.
Work out how much interest Cara will pay altogether.

9 Sam earns $54 275 in a year.
He pays no income tax on the first $8200.
He pays 18% income tax on everything he earns over $8200.
a Work out how much income tax he pays.
b Work out what percentage of his income he pays in tax.
c If the income tax rate is increased to 21%, how much more tax will Sam pay?

10 The price of a second-hand car is $6975.
Which of the three offers on the right is the best offer? $900 reduction 15% discount
Give a reason for your answer.
Pay just seven-eighths
11 Kate bought 12 bottles of perfume for $145 altogether and sold
them all at $18.50 each.
Work out her profit or loss. Give your answer as a percentage.
12 An antiques dealer bought three items and then sold them.
The prices are shown in the table. Item Clock Necklace Picture
a Work out the percentage profit or loss for each item.
b Work out the overall percentage profit or loss Buying price $120 $42 $890
for all three items together. Selling price $205 $95 $725

Summary

You should now know that: You should be able to:
+ Percentages can be written as fractions or + Extend mental methods of calculation, working
decimals. This is be useful when making mental with decimals, fractions, percentages and factors,
calculations. using jottings where appropriate.
+ Fractions and percentages are a good way to + Recognise when you need to use fractions or
compare different quantities. percentages to compare different quantities.
+ You can solve problems involving percentage + Solve problems involving percentage changes,
changes. choosing the correct number to take as 100% or
+ You can solve problems involving profit and loss, as a whole, including simple problems involving
interest, discount, interest and income tax. personal and household finance, for example,
simple interest, discount, profit, loss and tax.
+ You can solve problems involving percentages,
either mentally or with a calculator. + Calculate accurately, choosing operations and
mental or written methods appropriate to the
numbers and context.

108 11 Percentages