101st Group

101st Group
Group the consecutive counting numbers as follows: (1), (2, 3), (4, 5, 6), (7, 8, 9, 10), . . Notice that there is one number in the first group, two numbers in the second group, three in the third, etc. What is the sum of the numbers in the 101st group?
Source: mathcontest.olemiss.edu 10/17/2011

This problem is similar to problem “199 Numbers” dated 3/12/2007 and to problem “Consecutive Counting Groups” dated 1/18/2010. Please see them for solution.

Answer: 515201.


About mvtrinh

Retired high school math teacher.
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