Back to: PRIMARY SIX MATHEMATICS LESSON NOTES AND LESSONS SET ONE

Square, triangular and even numbers

**Triangular numbers**

These are numbers got after adding consecutive counting numbers e.g.

4

1 = 1,

1 +2 = 3,

1 + 2 + 3 = 6

1+2 + 3 + 4 = 10

1+2 + 3 + 4 +5 = 15

1+2 + 3 + 4+ 5 + 6 = 21

1+2 + 3 + 4 + 5 + 6 + 7= 28

1+2 + 3 + 4 + 5 + 6 + 7 + 8=36

1+2 + 3 + 4 + 5 + 6 + 7 + 8+ 9 = 45

1+2 + 3 + 4 + 5 + 6 + 7 + 8+ 9 + 10 = 55

The triangular numbers are {1,3, 6,10,15, 21,28,36,45,55 …}

**Square numbers**

A square number is a number got after multiplying a counting number by itself. e.g.

1 x 1 =1

2 x2 =4

3×3 = 9

4 x 4 = 16

5 x 5 = 25

6 x 6 = 36

NB; try it with other counting numbers up to 20

**Even numbers**

These are numbers which are exactly divisible by 2. e.g. 0, 2, 4, 6, 8, 10, …

All numbers that end with 0,2,4,6 and 8 all even numbers.

**Odd numbers**

These are numbers which are not exactly divisible by 2 e.g.1, 3, 5, 7, 9,11,13,15, …

**Whole numbers**

Whole numbers are all counting numbers with zero e.g. 0,1,2,3,4,5,6, …

Counting / Natural numbers

These are all positive numbers on a number line e.g. 1, 2, 3, 4, 5,6, 7, …

**Activity**

- List all the triangular numbers less than 30 (show your working)
- List the triangular numbers less than 40 which are divisible by 3.
- What is the sum of all numbers from 1 to 10?
- Find the value of the unknown

a) 1 x 1 = a

b) 2 x 2 = k

c) 4 x k=16

d) 13 x b = 169 - List elements in a set of counting numbers from 15 to 24
- Write the counting numbers between 10 and 30 which are divisible by 3.
- List elements in a set of even numbers below 20.
- What is the first even number?
- List members in a set of odd numbers divisible by 3 less than 30
- List the prime numbers between 10 and 30
- What is the difference between the prime numbers between 30 and 40?