1. Form 1 Mathematics Chapter 1
Directed Numbers
Form 1 Mathematics
Chapter 1

2. Extra Tutorial List
Marks in Open Book Quiz < 30 and Marks in Close Book Quiz < 30
9 students
Class numbers:
1, 7, 12, 14, 16, 17, 19, 24, 31
If any student wants to join, please talk to me privately. (Now, 4 students)
Every Tuesday CTPs (Last Lesson)

3. Introduction to Directed Numbers
Numbers have two parts:
Size or Magnitude
Sign or Direction
In the figure:
– 4 F

4. Examples of Directed Numbers
What does the negative mean?
Money in bank:
+$1,100 – $950
Students in class (36 students in class)
Mon: – 2; Tue: – 1; Wed: 0; Thu: – 3; Fri:0
World time:
Sydney: +2; Rome: – 6; London: – 8; New York: – 13
Stairs in the building (up is “+”):
Go up 3 steps: +3; Go down 4 steps: – 4

5. The Four Basic Operations
Addition:
Say “3 plus 7” or “The sum of 3 and 7” or “Add 3 to 7”
Subtraction: 3 – 7
Say “3 minus 7” or “The difference of 3 and 7” or “Subtract 7 from 3”
Multiplication: 3 × 7
Say “3 times 7” or “The product of 3 and 7” or “Multiply 3 and 7”
Division: 3 ÷ 7
Say “3 divided by 7” or “The quotient of 3 and 7” or “Divide 3 by 7”

6. Rules to Remember (p.50) ( + ) ( + ) = ( + ) ( – ) ( – ) = ( + )
( + ) ( + ) = ( + ) ( – ) ( – ) = ( + )
( + ) ( – ) = ( – ) ( – ) ( + ) = ( – )
正正得正 負負得正
正負得負 負正得負

7. Addition and Subtraction
+3 + (+9) =
( + ) ( + ) = ( + )
( – ) ( – ) = ( + )
( + ) ( – ) = ( – )
( – ) ( + ) = ( – )
= 12
–7 + (+12)
= –7 + 12
= 5

8. Addition and Subtraction
+3 + (– 9)
= 3 – 9
( + ) ( + ) = ( + )
( – ) ( – ) = ( + )
( + ) ( – ) = ( – )
( – ) ( + ) = ( – )
= – 6
7 – (+12)
= 7 – 12
= – 5

9. Addition and Subtraction
– 6 + (– 7)
= – 6 – 7
( + ) ( + ) = ( + )
( – ) ( – ) = ( + )
( + ) ( – ) = ( – )
( – ) ( + ) = ( – )
= – 13
– 3 – (+3)
= – 3 – 3
= – 6

10. Addition and Subtraction
7 – (– 7) =
( + ) ( + ) = ( + )
( – ) ( – ) = ( + )
( + ) ( – ) = ( – )
( – ) ( + ) = ( – )
= 14
– 3 – (–3)
= – 3 + 3
= 0

11. Rules to Remember (p.50) ( + ) ( + ) = ( + ) ( – ) ( – ) = ( + )
( + ) ( + ) = ( + ) ( – ) ( – ) = ( + )
( + ) ( – ) = ( – ) ( – ) ( + ) = ( – )
正正得正 負負得正
正負得負 負正得負

12. Multiplication 3  4 = 12 2  4 = 8 1  4 = 4 0  4 = 0 – 1  4 = ?
3  4 = 12
2  4 = 8
1  4 = 4
0  4 = 0
– 1  4 = ?
– 2  4 = ?
( + ) ( + ) = ( + )
( – ) ( – ) = ( + )
( + ) ( – ) = ( – )
( – ) ( + ) = ( – )
– 4
– 8

13. Multiplication 3  (– 5) = – 15 2  (– 5) = – 10 1  (– 5) = – 5
3  (– 5) = – 15
2  (– 5) = – 10
1  (– 5) = – 5
0  (– 5) = 0
– 1  (– 5) = ?
– 2  (– 5) = ?
( + ) ( + ) = ( + )
( – ) ( – ) = ( + )
( + ) ( – ) = ( – )
( – ) ( + ) = ( – ) 5 10

14. Multiplication (+ 7)  (+ 7) = 7  7 = 49 (– 8)  3 = – 8  3 = – 24
= 7  7
( + ) ( + ) = ( + )
( – ) ( – ) = ( + )
( + ) ( – ) = ( – )
( – ) ( + ) = ( – )
= 49
(– 8)  3
= – 8  3
= – 24
Same as (– 8) + (– 8) + (– 8) = (– 24)

15. Multiplication 4  (– 2) = – (4  2) = – 8 (– 8)  (– 7) = + (8  7)
= – (4  2)
( + ) ( + ) = ( + )
( – ) ( – ) = ( + )
( + ) ( – ) = ( – )
( – ) ( + ) = ( – )
= – 8
(– 8)  (– 7)
= + (8  7)
= 56
Note: (– 8)  (– 7) = (– 8) (– 7)

16. Time for Practice Page 56 of Textbook 1A Page 62 of Textbook 1A
Class Practice
Page 62 of Textbook 1A
Questions 1 – 2

17. Rules to Remember (p.50) ( + ) ( + ) = ( + ) ( – ) ( – ) = ( + )
( + ) ( + ) = ( + ) ( – ) ( – ) = ( + )
( + ) ( – ) = ( – ) ( – ) ( + ) = ( – )
正正得正 負負得正
正負得負 負正得負

18. Division (+ 7)  (+ 7) = 7  7 = 1 (– 9)  3 = – 9  3 = – 3
= 7  7
( + ) ( + ) = ( + )
( – ) ( – ) = ( + )
( + ) ( – ) = ( – )
( – ) ( + ) = ( – )
= 1
(– 9)  3
= – 9  3
= – 3
Note: (– 9) = (– 3) + (– 3) + (– 3)

19. Division 4  (– 2) = – (4  2) = – 2 (– 12)  (– 6) = + (12  6) = 2
= – (4  2)
( + ) ( + ) = ( + )
( – ) ( – ) = ( + )
( + ) ( – ) = ( – )
( – ) ( + ) = ( – )
= – 2
(– 12)  (– 6)
= + (12  6)
= 2

20. Time for Practice Page 59 of Textbook 1A Page 62 of Textbook 1A
Class Practice
Page 62 of Textbook 1A
Questions 3 – 4

21. Reminder Extra Tutorial Standard Homework (II)
9 Oct (Tue)
9 students (Must) + 4 students (Voluntary)
Standard Homework (II)
10 Oct (Wed)
Open Book Quiz (Chapter 1)
Close Book Quiz (Chapter 1)
17 Oct (Wed)

22. Enjoy the world of Mathematics!
Good Luck!
Enjoy the world of Mathematics!
Ronald HUI