Question 7
A glass jar contains 1000 g of a 10% poison solution. The solution is poured into another container, leaving 0.1% of the solution in the jar. The jar is then rinsed repeatedly with distilled water. At each rinse the poison mixes completely with the water, but after pouring, 0.1% of the mixture remains. How many rinses are needed to leave at most $1/10^{12}$ g of poison, if each rinse uses 1000 g of distilled water?
