Math Olympiad Problem

Question

Pat reads 1 page of a certain novel every Monday, 2 pages every Tuesday, 3 pages every Wednesday, and so on up to 7 pages every Sunday. She reads every page exactly once and does not skip any days. Suppose Pat starts reading page 1 on a Monday and reads the pages in order. On which day of the week does she read page 100?

Answer 1

interesting twist. simply find the day and mod by 7

sum(i) from 1 to n = (n*(n+1)/2

looking at the values, the 105th page is read on the 14th day, so the second sunday