Dr Yeap Ban HarConsultant, New Syllabus Mathematics
Junyuan Secondary School,
Singapore
Victory Christian International School,
Manila
1st Block 4 x 2 x 12nd Block 4 x 2 x 33rd Block
Method 1
21 + 23 + 25 = 6919 + 21 + 23 = 6317 + 19 + 21 = 57
Method 2
Note that the mean of the three numbers is the middle number
57 : 3 = 19The other numbers are 17 and 21.
Method 3
Make a list 1, 3, 5, 7, 9, …, 15, 17, 19, 21, 23, 25, 27, …
Method 3
x
x
x
2
2 2
The numbers are 17, 19 and 21.
Lesson 41 10.10.11
ab To prove that angle at centre
is equal to 2a + 2b
a
Northbrooks Secondary School,
Singapore
Lesson 41 10.10.11
ab To prove that angle at centre
is equal to 2a + 2b
a
2a
180o - 2a
Lesson 41 10.10.11
ab To prove that angle at centre
is equal to 2a + 2b
a
2ab2b
Lesson 42 10.10.11
a b
In the case of this type of figures, where is the angle at centre?a
2a
b
2b