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Pui Ying College
F.1 Mathematics
Chapter Ten --- Percentages
Supplementary Exercise
Name: ______________
Class: __________ ( )
Date: _______________
Exercise 10.1
1.
2.
There are 200 Form One students in a school. 68 of them are wearing
glasses.
(a) What percentage of them are wearing glasses?
34%
(b) What percentage of them are not wearing glasses?
66%
The total cost of a box of candies includes material cost, labour cost and 20%
advertising cost. If the material cost and labour cost are respectively
11
and 0.36 of the total cost, what percentage of the total cost is the
25
advertising cost?
3.
In an English test, Kenny got 56 out of the total mark 70. In a
Mathematics test, he got 60 out of the total mark 80.
(a) What was his mark in percentage in the English test?
(b) What was his mark in percentage in the Mathematics test?
(c) In which test did Kenny have a better result?
80%
75%
English test
Exercise 10.2
1.
There are 20 magazines on a shelf. 40% of them have a red cover. How
many magazines have a red cover?
8
2.
In a box of electronic parts, 10% are defective. If there are 11 defective
pieces, how many pieces of electronic parts are there in the box?
110
3.
Johnny spent 40% of his savings to buy a pair of shoes. If the pair of
shoes cost $720, how much were his savings originally?
$1800
4.
In an exhibition of a famous photographer, 40% and 35% of the
photographs were landscapes and portraits respectively. The rest were 50
photographs of buildings.
(a) What percentage of the photographs were buildings?
(b) How many photographs were there totally in the exhibition?
(c) If 20% of the portraits were children, how many portraits of
children were there?
25%
200
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1
Exercise 10.3
1. The cost of a watch is $400. If the selling price is $450, what is the profit
12.5%
rate?
2. The cost of a book is $60. If it is sold at $48, what is the loss rate?
20%
3. The cost of a bottle of medicine is $24. If it is sold at a profit rate of 35%,
what is the selling price?
$32.4
4.
The cost of a vase is $800. It is sold at a loss rate of 70% because of some $240
defects on the surface. What is the selling price?
5.
If a model ship is sold at $180, the profit is $30. Find the profit rate.
20%
6.
A necklace is sold at $200. If the profit rate is 150%, find the cost of the
necklace.
$80
7.
An outdated computer game is sold at $90. If the loss rate is 40%, find the $150
cost of the computer game.
8.
The marked price of a pair of scissors is $75. If it is sold at 20% discount, $60
what is the selling price?
9.
The marked price of a new brand of fruit juice is $7.6 per bottle. 50%
discount is offered in the promotion period. What is its selling price per
bottle?
10. The marked price of a sweater is $960. If it is sold at $900, what is the
discount rate?
$3.8
6.25%
11. Mrs. Wong bought a pair of shoes at 20% discount. If she bought the shoes $840
at $672, find the marked price.
12. A flower shop bought 40 roses at $320. The first 30 of them were sold at
$15 each. The other 10 roses were sold at $5 each.
(a) Find the profit rate of the first 30 roses.
(b) Find the loss rate of the other 10 roses
(c) Find the total profit rate or loss rate of the 40 roses.
87.5%
37.5%
56.25%
Exercise 10.4
1.
Barbara has deposited $5000 in a bank. The annual simple interest rate is
6%. How many years later will she get an interest of $1200?
4 years
2.
Amy has deposited $8500 in a bank. She will get a simple interest of
$1020 one and a half years later. What is the annual interest rate?
8%
3.
Jerry has deposited $3000 in a bank. The annual simple interest rate is 9%. 3.5 years
How many years later will he get the amount of $3945?
4.
Mandy has put $55000 in a 1-month fixed deposit account. The annual
$ 1954
interest rate is 6%. If the principal plus the interest are renewed at the end
of each period, find the interest she will get 7 months later. (Given the
answer correct to the nearest dollar).
2
Exercise 10.5
1.
The value of a stamp is now $1200. If its value increases by 20%
annually, find its value 3 years later. (Give the answer correct to the
nearest integer.)
$ 2074
2.
The number of residents in a new town increases by 10% annually. If
there are now 80000 residents, how many residents will there be 4
years later? (Given the answer correct to the nearest integer)
117 128
3.
In a district with an aging population, the number of students decreases 20 577
by 5% annually. If there are now 24000 students, find the number of
students 3 years later. (Given the answer correct to the nearest integer)
4.
In this school year, the scores of Alex in mathematics tests have been
56
decreasing by 20% each time. If his score in the third test was 36, what
was his score in the first test? (Given the answer correct to the nearest
integer)
5.
The monthly salary of Joseph has been increasing by 20% annually. If
his monthly salary is now $13824,
(a) find his monthly salary 3 years ago.
$8000
(b) how many years later will his monthly salary be over $20000?
3 years later
6.
The number of crimes in a district has been decreasing by 10% per
month because of new fight-crime policies. If there were 2916 crimes
in July,
(a) how many crimes were there in April in the same year?
4000
(b) in which month would the number of crimes be less than 2000?
November
Revision Exercise 10
1.
2
16 % can be expressed as
3
1
6
2.
Mr. Ho has deposited $20000 in a bank at an annual interest rate of $1272
6%. If the interest is compounded yearly, the interest that he will get
in the second year is
3.
Mr. Lam spends $1680 on traffic every month. This is 6% of his
$28 000
monthly salary. How much is his monthly salary?
4.
The cost of a product is $400. If the profit rate in selling this product $560
is 40%, find the selling price.
5.
The selling price of a doll is $160 and the profit rate is 150%.
(a) Find the cost of the doll.
(b) Find the profit.
$64
$96
6. A hawker bought in some cabbages and some celery. The total cost of
the cabbages was $120 and they were sold at a profit rate of 40%.
The celery was sold at a loss rate of 30% for a total of $119.
(a) Find the total selling price of the cabbages.
$168
(b) Find the total cost of the celery.
$170
3
(c) Consider all the cabbages and celery together. How much was
the profit or loss? What was the profit rate or loss rate?
7.
Loss $3
Loss rate 1
1
%
29
A fruit shop bought in 80 oranges for $360, and then sold them at a
marked price of $6 each. 50% of the oranges were sold at the marked
price, 40% of the oranges were sold at 20% discount, and the rest
were sold at 30% discount.
(a) What would the profit rate be if all the oranges were sold at the
1
33 %
3
marked price?
(b) What was the total selling price of all the oranges?
$427.2
(c) What was the net profit rate in selling all the oranges?
2
18 %
3
Extra Exercise
1.
The capacity of a water tank is 350L. 42% of it is now filled with
water.
(a) How much water is there in the tank now?
(b) How much more water is needed to fully fill the tank?
147L
203L
2.
A fruit shop bought 10 dozens of mangoes at $400. The shop then 50%
sold them at $5 each. Find the profit rate.
3.
The selling price of a chair is $726. If the profit rate is 32%, what is 550
its cost?
4.
In the big sales of a boutique, shirts were sold at a loss rate of 30%,
and skirts were sold at a loss rate of 50%. If the cost of a shirt were
$160, and the selling price of a skirt was $120, find
(a) the selling price of a shirt,
112
(b) the cost of a skirt,
240
(c) the overall loss rate in selling a shirt and a skirt.
42%
4