Question

Find the 30th triangular number, which
is TR (30).

Answer 1

Explanation:

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Answer 2

30th triangular number = 465

Explanation:

the rule for calculating any triangular number is

`a_(n)` =
`(1)/(2)` n(n + 1)

so to find the 30th triangular number, substitute n = 30 into the rule

a₃₀ =
`(1)/(2)` × 30 × (30 + 1) = 15 × 31 = 465