It takes five days for a ship to sail from Chongqing to Shanghai and seven days from Shanghai to Chongqing. So how many days does it take for a wooden sign to flow from Chongqing to Shanghai? (Mathematical problems Firstly, assume that the ship speed must be X/ day, the current must be A/ day, and the whole length is s; (X+A)*5T=(X-A)*7T =S

X=6A

S=(6A+A)*5T=(6A-A)*7T=35T*A

So it takes 35 days. ...

Welcome to Chongqing Wudoumi! ! !