Author |
Topic: How wide is the river? (Read 331 times) |
|
otter
Junior Member
Gender: 
Posts: 142
|
 |
How wide is the river?
« on: May 20th, 2003, 9:03pm » |
 Quote  Modify
|
Two ferries start at the same time from opposite sides of a river, travelling across the water on routes lying at right angles to the shores. Each boat travels at a constant speed, but their respective speeds are different. They pass at a point 720 yards from the nearer shore. Both boats remain at their piers for 10 minutes before starting the return trip. On the return, they meet 400 yards from the other shore. How wide is the river?
|
|
 IP Logged |
We shall not cease from exploration. And the end of all our exploring will be to arrive where we started
and know the place for the first time.
T.S. Eliot
|
|
|
ThudnBlunder
wu::riddles Moderator
Uberpuzzler
The dewdrop slides into the shining Sea
Gender:
Posts: 4489
|
|
Re: How wide is the river?
« Reply #1 on: May 21st, 2003, 1:37pm » |
Quote Modify
|
This is an oldie.
As both ferries wait at the pier for the same amount of time, this period can be ignored.
Let width of river = W
When the ferries first meet, they have travelled an aggregate distance of W, the width of the river.
When they next meet, they have travelled an aggregate distance of 3W.
As they travel at constant speeds, we can conclude that the distances each ferry
has travelled upon their two meetings are also in the ratio 3:1
Hence (W + 400) / 720 = 3
So W = 1760 yards = 1 mile
|
| « Last Edit: May 22nd, 2003, 6:07am by ThudnBlunder » |
IP Logged |
THE MEEK SHALL INHERIT THE EARTH.....................................................................er, if that's all right with the rest of you.
|
|
|
|
RIDDLES SITE
WRITE MATH!
Home 
Help 
Search 
Members 
Login 
Register
Reply
Notify of replies
Send Topic
Print