year 8 maths

264 Chapter 4 Fractions, decimals, percentages and financial mathematics
1 The side length of a cube is increased by 20% . As a percentage, by how much does its volume change?
Puzzles and challenges
2 The cost of an item in a shop increased by 20% and was later decreased by 20% at a sale. Express the
final price as a percentage of the original price.
1
3 Evaluate
2 × 2 3 × 3 4 × 4 5 × … × 999 without using a calculator.
1000
4 Some prize money is shared between three students. Abby receives 1 4 of the prize, Evie 1 and Molly
3
the remainder. If Molly is given $20, what is the total value of the prize money?
5 Freshly squeezed orange juice contains 85% water. A food factory
has 100 litres of fresh orange juice which is then concentrated by
removing 80% of the water. What percentage of water is in the
concentrated orange juice?
2
6 On line segment AD, AC is
3 of AD and BD is 3
of AD . What
4
fraction of AD is BC ?
?
A
B
C
D
7 Fifty people surveyed said they like apples or bananas or both. Forty per cent of the people surveyed
like apples and 70% of the people like bananas. What percentage of people like only apples?
8 A bank balance of $100 has 10% of its value added to it at the end of every year, so that at the end of
the second year the new balance is $110 + $11 = $121 .
How many full years will it take for the balance to be more than $10 000 ?
9 From the time Lilli gets up until her bus leaves at 8:03 a.m., she uses one-fifth of the time having a
shower and getting dressed, then one-quarter of the remaining time packing her lunch and school bag,
one-third of the remaining time having breakfast and then one-half of the remaining time practising
the piano, which she finishes at exactly 7:45 a.m. At what time does Lilli get up?
10 Four numbers, a, b, c, d, are evenly spaced along a number line. Without using a calculator, find the
values of b and c as fractions, given that:
1
a a = −1
3 , d = 1 7
b a = 1
6
20 , d = 2 1
5
Cambridge Maths NSW
Stage 4 Year 8 Second edition
ISBN 978-1-108-46627-1 © Palmer et al. 2018
Cambridge University Press
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