Q: 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?
A: 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 is 360.

Q: A total of 42 baby sea turtles hatched and are headed to the ocean. One-third of them got swept to the sea by a wave. How many are still on the sand?
A: This many baby turtles are in the ocean: 42 / 3 = 14 turtles. This many baby turtles are still on the sand: 42 - 14 = 28 turtles. The answer is 28.

Q: Roger rode his bike for 2 miles this morning, and then 5 times that amount in the evening. How many miles did Roger ride his bike for?
A:
Roger rode for 2 miles in the morning, and then 5 times that in the evening for 5 * 2 = 10 miles ridden in the evening. In total, that means Roger rode 2 + 10 = 12 miles over the course of the day. The answer is 12.