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Form 1 Mathematics Chapter 2 and Chapter 4 Correction of Open Book Quiz (Chapter 1) ◦ ◦ ◦ Today!!! Correction and Parent Signature of Close Book Quiz (Chapter 1) 24 Oct (Wed) Standard Homework (I) – Orange 24 Oct (Wed) You must hand in on time! Result of Close Book Quiz ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ Full mark: 36 (not 40!) and 10 bonus Highest: 44 Lowest: 11 Average: 24.7 Number of students below 20: 11 Major Problems Careless Mistakes! Wrong calculations! No English answers Result of Close Book Quiz 5th place: LAW Cheuk Hang Ellis WONG Pui Yin, Paul 4th place: WU SHAN Hao Yi 3rd place: FU Ling Yin 2nd place: LI Ming Chun Edward 1st place: LI Sai Kong Congratulations!!!!!! Well done!!!!!! Restaurant problem: ◦ 3 students went to a restaurant for a meal of $250. ◦ Everyone firstly paid $100. So, totally $300 ◦ When the waiter came back with $50, they decided to get $30 back (everyone gets $10 back) and then left $20 for tips. ◦ So, every student paid $90 only. Now, $90 x 3 + $20 = $290! Where is the last $10? Money is there! Only the calculation is wrong! The money given by the students (-) ◦ $90 x 3 = $270 The money goes to (+) ◦ $250 (to meal) + $20 (to waiter) = $270! So, the information is correct. The only problem is we have mixed up the calculation! If we can understand better Directed Number, we will not have this problem! Arithmetic Operations “+” – Addition ◦ Add… to… Difference Times Product Over Quotient “” – Division ◦ Divide… by… Minus “x” – Multiplication ◦ Multiply… by… Sum “–” – Subtraction ◦ Subtract… from… Plus “=“ – Equals/ is equal to Ronald HUI (+)(+)=(+) (+)(–)=(–) 正正得正 正負得負 (–)(–)=(+) (–)(+)=(–) 負負得正 負正得負 (+ A) + (+ B) = A + B (+ A) + (– B) = A – B (– A) + (+ B) = – A + B (– A) + (– B) = – A – B (+)(+)=(+) (–)(–)=(+) (+)(–)=(–) (–)(+)=(–) (+ A) – (+ B) = A – B (+ A) – (– B) = A + B (– A) – (+ B) = – A – B (– A) – (– B) = – A + B (+ A) (+ B) = A B (+ A) (– B) = – (A B) (– A) (+ B) = – (A B) (– A) (– B) = A B (+ A) (+ B) = A B (+ A) (– B) = – (A B) (– A) (+ B) = – (A B) (– A) (– B) = A B (+)(+)=(+) (–)(–)=(+) (+)(–)=(–) (–)(+)=(–) Consider A as a variable (變數) We know 3A = A + A + A or 3A = 3 A So, can we write: A 7 = A7 or A 7 = 7A ? Which is correct: B A = BA or B A = AB ? How about: 3A 4B? 3A4B / 12AB / 12BA / AB12 What if -3A -4B? Ronald HUI Pay attention to the followings: Consider A as a variable (變數) 1A=A A + A + A = 3A A A A = A3 3A 4A = 12A2 Ronald HUI When we work on the followings, we should put together the like terms and then simplify! For examples: 1. A +2B +3A +4B = A +3A +2B +4B = 4A + 6B 2. A -2B –3A +4B = A -3A -2B +4B = (A-3A) + (-2B+4B) = (-2A) + (2B) = -2A +2B Ronald HUI Page 77 of Textbook 1A ◦ Class Practice Addition of equality (等量相加) X–7=2 X -7 +7 = 2 +7 X=9 X–7=2 X = 2 +7 X=9 Ronald HUI Subtraction of equality (等量相減) X + 7 = 12 X +7 - 7 = 12 -7 X=5 X + 7 = 12 X = 12 -7 X=5 Ronald HUI Multiplication of equality (等量相乘) X5=4 X 5 5 = 4 5 X = 20 X5=4 X=45 X = 20 Ronald HUI Division of equality (等量相除) 5X = 20 5X 5 = 20 5 X=4 5X = 20 X = 20 5 X=4 Ronald HUI Page 91 of Textbook 1A ◦ Class Practice Use a letter x to represent unknown number 設 x 為變數 (即想求的答案) Follow the question and form an equation 根據問題,製造算式 Solve for x 算出 x 的值 Write answer in words (with units!) 寫出答案 (包括單位) Ronald HUI If the sum of 3 consecutive (連續) numbers are 69, find these numbers. Let x be the smallest number. Then, x+1 and x+2 are the next 2 numbers Then, x + (x+1) + (x+2) = 69 x + x +1 + x + 2 = 69 x + x + x + 1 + 2 = 69 3x = 66 => x = 22. So, the numbers are 22, 23 and 24. Ronald HUI Page 99 of Textbook 1A ◦ Questions 3 – 9 Correction of Open Book Quiz (Chapter 1) ◦ ◦ ◦ Today!!! Correction and Parent Signature of Close Book Quiz (Chapter 1) 24 Oct (Wed) Standard Homework (I) – Orange 24 Oct (Wed) You must hand in on time! Good Luck! Enjoy the world of Mathematics! Ronald HUI