Newton was the most famous mathematician in England in the17th century. He not only dares to explore profound mathematical theories, but also attaches great importance to the popularization of mathematical education. He once wrote a set of mathematics textbooks specially for middle school students. Newton thought: "When studying science, topics are more useful than rules." Therefore, many complicated and interesting math problems are arranged in the book to exercise students' mathematical thinking ability. The following topic is a famous exercise in the book.

"There are three grasslands with an area of 3 hectares, 10 hectares and 24 hectares respectively. The grass on the grass is as thick and grows as fast. If the first grassland can feed 12 cows for 4 weeks and the second grassland can feed 2 1 cow for 9 weeks, how many cows can the third grassland feed 18 weeks? "

This topic is really complicated and interesting. Because in a few months, new grass will grow on the grassland where cattle eat, and the growth of this grass will change with the length of time and the size of the area!

Newton devoted himself to this subject and found several different solutions. He thinks the following proportional solution is the most interesting.

First of all, suppose that the grass on the grassland will not grow after being eaten by cattle. Because "3 hectares of grassland can feed 12 cows for 4 weeks", according to this ratio, 10 hectares of grassland can feed 8 cows 18 weeks, or 16 cows for 9 weeks.

In fact, grass will grow after being eaten by cows, so the title says: "10 hectare of grass can feed 4 cows for 9 weeks." Comparing these two conclusions, we will find that the same 10 hectare grassland can feed 2 1- 16 = 5 cows for the same 9 weeks.

The difference between these five cows shows that in the last five weeks of nine weeks, the new grass on 10 hectare grassland can feed five cows for nine weeks. In other words, you can feed 2.5 cows 18 weeks.

Then, how many cows can eat the new grass in the last 18 week 14 week 18 week 18 hectare grassland? 5∶ 14=2.5∶? It is not difficult to work out that the answer is 7 cows.

Next, comprehensively consider various situations of 18 weeks.

It has been calculated that assuming that grass does not grow, 10 hectare of grass can feed 8 cows 18 weeks; Considering the growth of grass, the new grass on 10 hectare grassland can feed 7 cows 18 weeks. Therefore, 10 hectare grassland can actually feed 8+7 = 15 cows 18 weeks. According to this ratio, it is not difficult to calculate how many cows can be fed in 18 weeks on 24 hectares of grassland.

10∶24= 15∶?

Obviously. "?" 36 is the answer to the whole question.