1. Percentages (I) Form 1 Mathematics Chapter 3

2. Reminder Folder Checking ▫26 Nov (Mon) – All Chapters 0, 1, 2 and 4! ALL Corrections ▫26 Nov (Mon) – All Chapters 0, 1, 2 and 4! ▫Close Book Quiz with Parent’s signature! Extra Tutorial ▫27 Nov (Tue) – based on Close Book Quiz result ▫Mon & Tue after-school – Consultation on G/F Open Book Quiz ▫28 Nov (Wed)

3. Reminder Term 1 Examination Syllabus ▫Chapter 0: Basic Mathematics ▫Chapter 1: Directed Numbers ▫Chapter 2: Using Algebra to Solve Problems (I) ▫Chapter 3: Percentages (I) ▫Chapter 4: Using Algebra to Solve Problems (II) Date of Term 1 Examination ▫12-12-12 (Wed) ▫8:30 am – 9:30 am (1 hour) ▫Room 104

4. Result of Close Book Quiz ▫Full mark: 40 and 10 bonus ▫Highest: 41 ▫Lowest: 6 ▫Average: 28.6 (Open Book: 21.1) ▫Number of students between 10 - 19: 3 ▫Number of students between 0 - 9: 1 Major Problems ▫Don’t understand well the question! Result of Close Book Quiz

5. 5 th place(5):CHAN Tsz Long, Sam FU Ling Yin KO Ka Chung Boston TANG Yiu Cheung Harald YUEN Tin Wai, Timmy 4 th place:LI Ming Chun Edward 2 nd place(2):WU SHAN Hao Yi LI Sai Kong 1 st place:CHOI King Shing, Walker Congratulations!!!!!! Well done!!!!!! Result of Close Book Quiz

6. Mathematics nearby Mr. Hui bought a new car with $100,000 He makes up the car well and then try to sell it at a better price. So, he marked up 50% (half). His friend wants to buy a car also and then he approached Mr. Hui. Mr. Hui decided to sell it to his friend at a “friendship price” of 50% (half) of the marked price. Did Mr. Hui gain, lose or no gain no loss?

7. What is Percentage? Percentage is a fraction with the denominator equal to 100. “%” is the symbol of percentage and often is called “Per cent”. Per cent means “per one hundred”. Percentages can be presented in decimals. e.g.

8. What is Percentage? In other words, a fraction or decimal can be converted to percentage. e.g.

9. Simple Percentage Problems “What is 25% of $800?” “What percentage of 24 apples is 6?” “15% of the number of staff of a company is 24. What is the number of staff of that company?” These are the examples of simple percentage problems. By using some simple calculation, we can find the answers..

10. Simple Percentage Problems What is 25% of $800? What percentage of 24 apples is 6?

11. Simple Percentage Problems Jacky participates in a 5-km race. He has finished 1800m already. What percentage of the whole race does Jacky not finish? The remaining distance that Jacky needs to run = 5km – 1800m = 5000m – 1800m = 3200m The percentage Jacky does not finish is Remark: same units!

12. Simple Percentage Problems In a concert held in the Hong Kong Stadium, there were 8344 female persons, which was 28% of the total persons. Given that there were 40000 seats, find the percentage of seats occupied. Let n be total number of persons in the concert. Percentage of seats occupied

13. Time for Practice Page 117 of Textbook 1A ▫Questions 3 - 13 Pages 54 - 55 of WB 1A ▫Questions 4 - 9

14. Percentage Increase New value > Original value E.g. The Hang Seng Index increases from 11500 to 12150. We also say that the Index is increased by 5.65%.

15. Percentage Decrease New value < Original value E.g. The price of a flat decrease from $2,200,000 to $1,804,000. We always say that the price of the flat is reduced by 18%.

16. Percentage Increase & Decrease Last year, Andy was 150cm tall. His height is increased by 20% this year. What is his height now? Increase or Decrease? His height now is

17. Percentage Increase & Decrease The price of a car was $160,000 last month. What is the price of the car this month if the price is decreased by 15%? Increase or Decrease? The price this month is

18. Percentage Change We can summarize the two formulae into one and call percentage change. If New value > Original value, then + If New value < Original value, then –

19. Percentage Change The temperature was 30  C in the afternoon and the temperature dropped to 27  C in the evening. Find the percentage change in the temperature. The percentage change So, the percentage decrease in the temperature is 10%.

20. Percentage Change The profit of a company increases from $450,000 last year to $540,000 this year. What is the percentage change in profit? The percentage change So, the percentage increase in profit is 20%.

21. Percentage Change If the length and the width of a picture increased by 30% and 40% respectively, find the percentage change in the area of the picture. Let x and y be the length and the width of the picture respectively. The original area of the picture = xy

22. Percentage Change The new area of the picture The percentage change So, the percentage increase in the area is 82%.

23. Time for Practice Page 127 of Textbook 1A ▫Class Practice Page 129 of Textbook 1A ▫Questions 6 – 14 Pages 57 - 58 of WB 1A ▫Questions 3 - 9

24. Reminder Folder Checking ▫26 Nov (Mon) – All Chapters 0, 1, 2 and 4! ▫ALL Corrections are needed! ▫Close Book Quiz with Parent’s signature! Standard Homework (I) and (II) ▫27 Nov (Tue) Extra Tutorial ▫27 Nov (Tue) – based on Close Book Quiz result ▫Mon & Tue after-school – Consultation on G/F Open Book Quiz ▫28 Nov (Wed)

25. Enjoy the world of Mathematics! Ronald HUI