Weight of Copper and Tin to Produce an Alloy of 30% Copper and 10% of Tin Date of Exam May 2016 Subject Mathematics, Surveying and Transportation Engineering Problem A given alloy contains 20% copper and 5% tin. How many pounds of copper and of tin must be melted with 100 lb of the given alloy to produce another alloy analyzing 30% copper and 10% tin? All percentages are by weight. A. 20.5 lb copper and 4.5 lb tin B. 17.5 lb copper and 7.5 lb tin C. 19.5 lb copper and 5.5 lb tin D. 18.5 lb copper and 6.5 lb tin Answer Key Click here to show or hide the Answer Key [ B ] Solution Click here to expand or collapse this section Copper $20(100) + 100C = 30(100 + C + T)$ $70C - 30T = 1000$ ← equation (1) Tin $5(100) + 100T = 10(100 + C + T)$ $-10C + 90T = 500$ ← equation (2) From equations (1) and (2) $C = 17.5 ~ \text{lbs}$ $T = 7.5 ~ \text{lbs}$ Answer: [ B ] Category College Algebra mixture problem Alloy of Copper and Tin Two Equations, Two Unknowns Log in or register to post comments