1. Percentages (I) Form 1 Mathematics Chapter 3

2. Reminder Folder Checking ▫26 Nov (Mon) – All Chapters 0, 1, 2 and 4! ▫All corrections – All Chapters 0, 1, 2 and 4! ▫All Close Book Quiz with Parent’s signature! Extra Tutorial ▫27 Nov (Tue) ▫1, 10, 11, 12, 14, 16, 26, 30, 36 ▫Mon & Tue after-school – Consultation on G/F Open Book Quiz ▫28 Nov (Wed)

3. What is Percentage? “%” is the symbol of percentage. Per cent means “per one hundred”. e.g.

4. 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!

5. 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

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

7. 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%.

8. Percentage Increase 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

9. 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%.

10. Percentage 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

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

12. 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%.

13. 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%.

14. 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

15. Profit and Loss Cost / Cost price is the value of the good that the merchant paid for. Selling price is the value of the good that the merchant got in selling the good. Marked price is the value of the good displayed in the shop.

16. Profit and Loss Case 1:A man bought 5000 cutters at $3.6 each and sold all of them at $6 each. Case 2:A fruit importer bought 1000 boxes of apples at $65 box and found that 150 boxes of them were rotten. He then sold the rest at a unit selling price of $72. Case 3:A merchant bought 30 bicycles for $15000 and sold them at $780 each. Case 4:Some T-shirts cost $5000 but re-sold at a selling price of $4000.

17. Profit Selling Price > Cost Price

18. Loss Selling Price < Cost Price

19. Profit and Loss A shop sold a car at the profit % of 20%. If the profit was $32000, what was the cost of the car? What was the selling price? Profit or Loss? Let n be the Cost Price. Then, So, the Selling Price is

20. Time for Practice Pages 134 - 135 of Textbook 1A ▫Class Practice Page 137 of Textbook 1A ▫Questions 7 – 19 Pages 61 - 62 of WB 1A ▫Questions 7 - 10

21. Discount Western style vs. Chinese style 88 折 = 12% off

22. Discount Marked Price > Selling Price

23. Discount A pair of scorer shoes is sold at 25% discount at a marked price of $650. Can Vincent buy the shoes if he has $500? Marked price = $650 Selling price of the shoes Since Vincent got $500, he can buy the shoes.

24. Discount A golden ring is sold at 30% discount with a selling price of $441.What is the marked price? Selling price = $441. Let n be Marked price. Then, So, the Marked price is $630.

25. Time for Practice Pages 141 of Textbook 1A ▫Class Practice Page 142 of Textbook 1A ▫Questions 3 – 10 Pages 65 - 66 of WB 1A ▫Questions 7 - 10

26. Reminder Standard Homework (I) and (II) ▫27 Nov (Tue) Standard Homework (III) and (IV) ▫28 Nov (Wed) Extra Tutorial ▫27 Nov (Tue) ▫1, 10, 11, 12, 14, 16, 26, 30, 36 ▫Mon & Tue after-school – Consultation on G/F Open Book Quiz ▫28 Nov (Wed) Standard Homework (V) ▫30 Nov (Fri)

27. Enjoy the world of Mathematics! Ronald HUI