Two boats start moving at the same time from opposite sides of a river. Both at right angles to the parallel shorelines. One boat is faster than the other so they meet 720 yards from the nearest shore. After arriving at their destinations, each boat remains for 10 minutes before starting on the return trip. Once again, each boat is travelling at the same speed as it did before and on this occasion, they meet 400 yards from the other shore.
How wide is the river?
2006-06-08 03:43:08 · 5 answers · asked by brainyandy 6 in Science & Mathematics ➔ Mathematics
The width of the river is 1 mile = 1760yards
Yes, let A be the faster boat leaving from shore A, and B the slower boat leaving from shore B. A will a travel a distance (720+x) yards from shore A to where they first meet while B travels 720 yards from shore B. A reaches shore B first and waits10min and then starts back, while B reaches shore A later and does the same thing and they meet 400 yards from shore A. Since they wait the same time and keep their speed constant we must have 720-400 = 320 = x. So the river = 720+720+320 = 1760 yards.
It's easy to see if you eliminate the wait time and imagine A turns around as soon as he reaches shore B. A will be distance x from shore B on the return trip when B is distance x from reaching shore A. So they must still travel the width of the river to meet 400 yards from shore A. So we must have x+400 = 720 as the distance B travels to reach shore A and then return to the 2nd meeting point. So x = 320 and the river is a mile wide,
2006-06-08 17:02:57 · answer #1 · answered by Jimbo 5 · 3⤊ 0⤋
No, it's not 1.8 yards or 800 yards. The boats are traveling with same speed as before does not mean they are traveling with same speed.
Let's assume the river is x yards wide. In the fast trip boat two traveled 720 yards. So both one traveled x-720 yards. Similarly, on the second trip, boat two traveled 400 yards. So, both one traveled x-400 yards.....
2006-06-08 12:00:11 · answer #2 · answered by organicchem 5 · 0⤊ 0⤋
The width of the shore is 800 yards,
Since if both are travelling from same speed, they will cover same distance, So 400 yards from each shore.
So above is the answer..
2006-06-08 11:15:48 · answer #3 · answered by shyamanand 1 · 0⤊ 0⤋
1760 yards (1 mile)
2006-06-08 12:02:18 · answer #4 · answered by injanier 7 · 0⤊ 0⤋
it must be
720/400 =1.8 yards
2006-06-08 10:53:09 · answer #5 · answered by babar 3 · 0⤊ 0⤋