1.04 Square and triangular numbers

Interactive practice questions

Write down the next $3$3 triangular numbers.

$1$1, $3$3, $6$6, $10$10, $15$15, $\editable{}$, $\editable{}$, $\editable{}$

Easy

Less than a minute

Beginning with the $eighth$ triangular number, write down the next $3$3 triangular numbers is this series.

Find the $6$6th triangular number.

Find the $9$9th triangular number.

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Identify and describe properties of prime, composite, square and triangular numbers.