Question

Find the 10th triangular number.​

Answer 1

Answer:

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Step-by-step explanation:

the 10th triangular number is 10 + 10 + 10 + 10 + 5 + 10. Another interesting way of adding the numbers is to add the first and the last, then the second and the second to last, and so on. This leads to (1+ 10) + (2 + 9) + (3+ 8) + (4 + 7) + (5 + 6). This simplifies to 11 + 11 + 11 + 11 + 11 = 55.