1. Learn to identify and describe triangular numbers10
8 9
567
Triangular Numbers
Learn to identify and describe triangular numbers
Mrs J’s Resource Creations ©

2. What do you think a triangular number is?
Do you remember how Square Numbers looked like squares?
Well Triangular Numbers look like triangles!
See ->
But we use dots to form the shape of a triangle. . .
Mrs J’s Resource Creations ©

3. Let’s Take a Closer Look at Some Triangular Numbers . . .
On a piece of paper, draw what you think the next one will look like.
Then turn to the person sitting next to you and see if you agree with each other.
I got . . .
Did you get the same?
Mrs J’s Resource Creations ©

4. Can you see the Pattern? 1 3 6 10
So 1, 3, 6, and 10 are triangular numbers.
Turn to the person sitting next to you and describe to one another what pattern you can see.
Remember to raise your hand and wait for your turn first!
Share how you would describe the pattern with your class.
Mrs J’s Resource Creations ©

5. Describing the Pattern of Triangular Numbers
2 Rows of dots
4 Rows of dots
3 Rows of dots
1 + 2 = 3
= 6
= 10
So each time we are adding an extra number in the sequence because we are adding an extra row.
each time the highest extra number we add will be 1 higher than the last highest number added. This is because there will be an extra dot in the new row added.

6. See if you can work out the next triangular numbers in the pattern. . .?
= 10
= 15 ? ? ? ? ?
= 21
= 28

7. Your Task: Activity Time
By drawing dots, using counters or just using the pattern rule by adding the number of rows each time, explore and record on your sheet as many triangular numbers as you can find.
You will be using the triangular numbers you find for a game afterwards. The more you find the better chance you have of winning.
GOOD LUCK!

8. Game Time
GAME INSTRUCTIONS
Get your triangular numbers ready for triangular number bingo!
On the grid of 10 boxes you will need to fill out the triangular numbers you found (one per box).
If you did not find 10 triangular numbers, you will now need to randomly add the rest of the numbers to you list at the bottom of the sheet to play
If you found more than 10 triangular numbers, you can only choose 10 of them for your bingo card.
Numbers called will be between ONLY. If you discovered a triangular number higher than 100, firstly WELL DONE, then let your teacher know.

9. Triangular Bingo
First person to cross out all of their numbers, stand up and call Bingo WINS! 15 45 66 3 28 1 91 6 78 45 55 10 36
That’s all of the triangular numbers under 100. Well done to those who found 10 or more triangular numbers!

10. Interesting Fact About Triangular Numbers
Add two neighbouring triangular numbers - what do you notice? ? 25 10 + 15 =
What’s special about these numbers? 3 + 6 9 =
They are Square Numbers! 6 16 + 10 =

11. Lesson Review
Triangular numbers are found from a pattern of dots that form a triangle.
Some triangular numbers are: 1, 3, 6, 10, 15, 21, 28, 36, So on.
By adding another row of dots and counting all the dots we can find the next number of the sequence.
Every time you add a row, there will be an extra dot in that new row.
Adding two triangular numbers that sit next to each other will equal a square number.

12. Thank You!
Thank you so much for your download. I truly appreciate your business. 
Terms of Use:
All pages of this packet are copyrighted. You may not create anything to sell or share based on this packet.
This packet is for one teacher use only. Do not share with colleagues. If they like the packet please send them to my TPT store. TPT is about teachers supporting teachers 
You are permitted to share the cover image of this packet on your blog or via social media as long as you link back to my store on TPT showcasing the product or link to the product. My store link is
To stay posted on FREEBIES and my other products , follow my store on TPT.
Mrs J’s Resource Creations ©

13. Special Thanks for the Graphics & Fonts By:
Andrea Gibson