Xiaojiang walks 50 meters per minute, Xiao Fang walks 60 meters per minute, and the river walks 70 meters per minute. Xiao Jiang and Xiao Fang started from the first place, Xiao Jiang started from the second place at the same time, and Xiao Jiang met Xiaojiang He in three minutes. How many kilometers is it between A and B?

(50+70) × 3 = 360m 360 ÷ (60-50) = 36min (60+70) × 36 = 4680m = 4.68km.

Solution: After Xiao He met Xiao Fang, he met Xiao Jiang in 3 minutes, which means Xiao He Xiao Jiang walked 360 meters in 3 minutes. The number 360 here is also the time when Xiao He and Xiao Fang met. Xiaofang has gone further than Xiaojiang. Divide the distance difference by the speed difference and you can know the time. That is, when Xiao Fang and Xiaohe met, they had already walked for 36 minutes, so the distance between the two places was 4068 kilometers.