Q) 2 boats are crossing the river from opposite sides. When they first meet, they are 720m from the near shore. When they reach the opposite shore, they stop for 10mins and cross the river again, but this time they meet 400m from the other shore. How wide is the river?
Thanks in advance. :)
When they first meet, the slowest boat has travelled a distance $d$ equal to 720, and the total distance the two boats have travelled combined is the width of the river $w$. The second time they meet, the combined distance travelled by both is $3w$. The slow boat has traveled a distance $3d$ equal to $w + 400$. So $w$ equals three times 720 minus 400 is 1760.