CAT 2021 Question Paper | Quant Slot 1

CAT 2021 Quant was dominated by Arithmetic followed by Algebra. In Arithmetic, the questions were dominated by topics like Speed-time-distance, Mixture and Alligations. This year, there was a surprise. The questions from Geometry were relatively on the lower side as compared to the previous years. There were 8 TITA Qs this year. Overall this section was at a medium level of difficulty.

Question 18 : 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

Video Explanation

Explanatory Answer

The natural numbers are divided into groups as (1), (2, 3, 4), (5, 6, 7, 8, 9), ….. and so on.
If you observe that the first group ends with 1², the second group ends with 2²and the third group ends with 3² 
Hence, the 15th group ends with 15² = 225.
The 14th group ends with 14² = 196.
Therefore, the 15th group contains (197, 198, . . . . . . . . . . ,225)
The sum of the numbers in the 15th group =\\frac{29}{2})(197 + 225) = 6119.

The question is " 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 "

Hence, the answer is '6119'

Choice A is the correct answer.

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