Square and triangle numbers

What this chapter teaches

A square number is a number of dots in a square, such as 4 rows of 4 dots. A triangle number is a number of dots in a triangle whose rows grow by one dot each time. Each new row has one more dot than the last, and two triangle numbers side by side make a square number.

Three questions to ask

There is no one right wording. Listen for the idea.

1. Why is 9 called a square number?
2. How many dots will the next triangle number have, and how did you work it out?
3. What do you get if you put the triangle numbers 6 and 10 together?

After the chapter, the learner can

• Draw dots to show the square numbers 1, 4, 9 and 16
• Find the next triangle numbers after 1, 3, 6 and 10