Question

What square number will we get if we add eighth and ninth triangular numbers

Answer 1

In order to solve this question you need to have the basic idea of the sequence of triangular number and how it is formed.

If you don't know that then no need to worry, I've attached an image for you showing how it works.

So, the sequence is : 1, 3, 6, 10, 15, 21, 28, 36, 45, ......

So, eighth and ninth triangular numbers are : 36 and 45.

Now the task is pretty simple. by adding these two get 36 + 45 = 81 which is a perfect square of 9.

So, the square number is 81.(Ans)

Answer 2

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Step-by-step explanation:

your answer is 81