IQ Brain Teaser #186

Mary was working in a chemistry lab with a mixture of chemicals that was 90% water and weighed 20 pounds. After returning to the lab from a weekend break, she calculated the mixture was now 50% water. How much does the mixture now weigh? For purposes of this puzzle, assume the non-water part of the mixture was not affected by evaporation. 2 pounds 4 pounds 6 pounds 8 pounds 10 pounds 12 pounds 14 pounds 16 pounds 18 pounds 20 pounds view results