# Puzzles

## Triangle numbers

Source: ATM Mathematics Teaching 239

Let \(T_n\) be the \(n^\mathrm{th}\) triangle number. Find \(n\) such that: $$T_n+T_{n+1}+T_{n+2}+T_{n+3}=T_{n+4}+T_{n+5}$$

If you enjoyed this puzzle, check out Sunday Afternoon Maths VI,

puzzles about triangle numbers, or a random puzzle.

puzzles about triangle numbers, or a random puzzle.