Buy a bicycle with 600 yuan, sell it with 700 yuan, buy it back with 800 yuan, and finally sell it with 900 yuan. How much do you earn? On this issue, I would like to say that if you buy a bicycle at a cost of 1000 yuan, sell it at 600700 yuan, buy it back at 800 yuan, and sell it at 900 yuan, the formula is 1000-600 + 700-800 + 900 = 1200, and you can earn 200 yuan But the first time you sell 900, and then you buy 800 back, you can actually buy 600. The formula is 1000-600 + 900-600 + 900 = 1600, and the final result is 1600-1200 = 400. I don't know whether my understanding is right or wrong Here I am saying to those who say that they are earning 200: losing money is not just losing money on the basis of the original plan. More often, you have to find out how to make more money with the greatest benefit. Earning 200 is earning, But you can make more money. Of course, the position of making 200 is in mathematics. Now we should think about it from various angles. Of course, my answer is not necessarily 100% right

If you follow the second method, you will earn 600 yuan. Your understanding is right, but you regret it