Question

The two consecutive triangular numbers are 15 and 21.



Explanation:

A triangular number is a number that is capable of forming a triangular dot pattern with the triangle being an equilateral triangle. The triangular number series is given as follows:



0, 1, 3, 6, 10, 15, 21, 28, 36, 45, 55, 66…



In the above series, each digit represents the number of dots in the triangle.


Thus, the square number 36 can be expressed as the sum of the two consecutive triangular numbers 15 and 21. In other words, 15 + 21 = 36.

Answer 1

Answer:

The original triangular number series is like “0, 1, 3, 6, 10, 15, 21, 28, 36, 45, 55, 66, 78, 91, 105, 120, 136, 153, 171…. “ When you look at the series, the number 15 and 21 are the two consecutive triangular numbers whose sum make the square 36 (15+21=36).18-