number · Year 6 · Suggested learning sequence
Square and triangular numbers
A square number makes a square of dots: 5 rows of 5 is 5 × 5 = 25. A triangular number makes a triangle: rows of 1, 2, 3, 4 add to 10. Square numbers go 1, 4, 9, 16, 25. Triangular numbers go 1, 3, 6, 10, 15. To get the next triangular number, add a new bottom row one longer than before. To get the next square, add a new row and a new column.
Sample questions
How many dots are in this square pattern? That is the square number it shows.
- The pattern has 4 rows with 4 dots in each row.
- 4 × 4 = 16, so it shows the square number 16.
Answer: 16
How many dots are in this square pattern? That is the square number it shows.
- The pattern has 3 rows with 3 dots in each row.
- 3 × 3 = 9, so it shows the square number 9.
Answer: 9
How many dots are in this square pattern? That is the square number it shows.
- The pattern has 5 rows with 5 dots in each row.
- 5 × 5 = 25, so it shows the square number 25.
Answer: 25