Quantitative Aptitude Question on Basics of Numbers

Question

The natural numbers are divided into groups as (1), (2, 3, 4), (5, 6, 7, 8, 9), …..and so on. Then, the sum of the numbers in the 15th group is equal to

Answer 1

Solution

The natural numbers are organized into sets like (1), (2, 3, 4), (5, 6, 7, 8, 9), and this pattern continues indefinitely.
If you notice that the initial set concludes at 12, the second set concludes at 22, and the third set concludes at 32.

As a result, the 15th set concludes with 152, which equals 225.
The 14th set concludes with 142, which equals 196.
So, the 15th set comprises the numbers from 197 to 225, inclusive.
The total of the numbers in the 15th set is $\frac{29}{2}(197 + 225)$ resulting in 6119.