Find the fifth triangular number.

Triangular number:

A triangular number counts objects arranged in an equilateral triangle.

$n^{th}$ triangular number is given by $\frac{n(n+1)}{2}$.

Fifth triangular number $= \frac{5(5+1)}{2} = \frac{5\times 6}{2} = 5\times3 = 15$.

Therefore, the fifth triangular number is 15. 

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Updated on: 10-Oct-2022

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