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ITOT 42 Autumn 2020 - THCS A - Additive practice Question 3

ITOT · ITOT 42 Autumn 2020 - THCS A - Additive practice

Question 3

On each turn Alice announces an integer $x$. Bob writes either $x$ or $x$ plus the sum of all numbers already on the board. Initially the board is empty. Can Alice force, after finitely many turns, (a) at least 100 occurrences of 5; (b) at least 100 occurrences of 10?