Big Dig Mining Company mines three different types of ore: copper, iron, and nickel. Across all their mines, 10% of their output is nickel, 60% is iron, and the rest is copper. They mine 720 tons of nickel a day. How many tons of copper does Big Dig Mining Company mine daily? Let's answer step by step:
Let R be the total ore output of the company. Of Big Dig's output, 100 - 10 - 60 = 30% is nickel. Since 720 is 60% of 100% of their output, 720 / R = 60 / 100. Thus, Big Dig mines R = 100 * 720 / 60 = 1200 tons of ore daily. Therefore, Big Dig mines 1200 * 30 / 100 = 360 tons of copper daily. The answer: 360.