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Problem 397

Combinatorics Difficulty 2.0 Find the answer UKMT Junior Kangaroo · United Kingdom · 2026

The integers 1 to 20 are written on a board. Patricia erases three of the integers and replaces them with their sum. She repeats this process until only two integers remain. What is the sum of these two remaining integers?

(A) $100$ (B) $150$ (C) $180$ (D) $200$ (E) $210$

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