Solution: It is known that three chickens lay three eggs in three days, 9=3×3, so the number of eggs laid by nine chickens in three days is 3× 3 = 9, and the number of eggs laid by nine chickens in nine days is 9× 3 = 27. A: Nine chickens laid 27 eggs in nine days.

Mathematics is produced by counting, calculating, measuring and observing the shape and motion of objects through abstract and logical reasoning. In many countries and regions, mathematics has become a part of education. It is applied in different fields, including science, engineering, medicine, economy and finance. Mathematicians also study pure mathematics, which is the substantive content of mathematics itself and does not aim at any practical application.

The benefits of learning math well

1. Mathematics is the basis of all re-education and an important channel for cultivating logical thinking. Don't just look at the present, think about the long term. Mathematics is the soul of all disciplines.

2. Mathematics is the foundation of all sciences, and all major scientific and technological progress is closely related to mathematics. Without mathematics, there would be no computers, televisions and space shuttles, and there would be no such colorful life today.

3. Mathematics is a tool discipline, which is the basis of learning other disciplines and also a discipline to improve people's ability of judgment, analysis and understanding.

Mathematics is not only a science, but also a universally applicable technology. It is the door and key to science. Learning mathematics is a very important measure to make oneself rational, and mathematics itself has its fun.