1. In a pile of 200 coins, $2 \%$ are gold coins and the rest are silver. Simple Simon removes one silver coin every day until the pile contains $20 \%$ gold coins. How many silver coins does Simon remove?
1. 180 The number of gold coins in the original pile is $0.02 \times 200=4$. These form $20 \%$ of the final pile. Therefore there are $4 \times 5=20$ coins left. Hence the number of silver coins Simon removes is $200-20=180$.