A Martin Gardner problem

  • #1
post your answers in white :biggrin: . no pen or paper allowed.

Two ferryboats start at the same instant from opposite sides of a river, traveling across the water on routes at right angles to the shores. Each travels at a constant speed, but one is faster than the other. They pass at a point 720 yards from the nearest shore. both boats remain in their slips for 20 minutes before starting back. On the return trips they meet 400 yards from the other shore.

How wide is the river?


I didn't get the right answer and then I felt like an idiot because the answer is really easy :frown: .
 

Answers and Replies

  • #2
30
0
The answer is:
1760
yards
 
  • #3
403
1
How wide is the river?
Well,
at the two moments the ferryboats meet, the relation between the distances covered by them is the same:
(w - a) / a = (2w - b) / (w + b)
So,
w = 3a - b = 3*720 - 400
w = 1760 yards

:smile:
 
  • #4
oops, totally forgot about this thread— yep, both right :biggrin: .
 

Related Threads on A Martin Gardner problem

  • Last Post
Replies
12
Views
2K
  • Last Post
Replies
7
Views
6K
  • Last Post
Replies
1
Views
1K
Replies
6
Views
3K
  • Last Post
Replies
2
Views
1K
  • Last Post
Replies
14
Views
2K
  • Last Post
5
Replies
120
Views
10K
  • Last Post
Replies
5
Views
3K
  • Last Post
Replies
2
Views
615
  • Last Post
Replies
1
Views
1K
Top