Only after growing up did I realize that the Ministry of Education was playing a big game.

When I was a child, there was a math problem: "Trains A and B depart from a place successively. So, how many hours later will Train A catch up with Train B?" Back then, I wondered why one train would chase another? For many years after doing that problem, I still didn't know why... But now I understand: the Ministry of Education and the Ministry of Railways have had a poor relationship for many years, and the Ministry of Education has never told the Ministry of Railways the answer.

When I was a child, there was a math problem: "A large pool has six pipes to fill it with water and eight pipes to drain it. How long does it take to fill the pool?" As a child, I thought if you want to fill the pool, just use the inlet pipes; if you want to empty it, just use the outlet pipes. Why open them at the same time? Isn't that wasting water resources and being un-environmentally friendly? I did this problem for many years and I still didn't know why... But now I understand: every rainy day, drainage facilities must be controlled well. Only in this way can cities without seas have the chance to see the sea.