In 1 kg mixture of sand and iron, 20% is iron. How much sand should be added so that the proportion of iron becomes 10%? a) 1 kg b) 200 gms c) 800 gms d) 1.8 kg e) None of these
Answer: A If we add x grams of sand, the total amount would be 1,000 + x grams of mixture and we need 200 grams of iron to be 10% of that: 0.1(1,000 + x) = 200 --> x = 1,000.