8. The Bobber
You can paddle your canoe seven miles per hour through any placid lake. The stream flows at three miles per hour. The moment you start to paddle up stream a fisherman looses one of his bobbers in the water fourteen miles up stream of you.
How many hours does it take for you and the bobber to meet?
Added 1 January 2007
Hint: Assume the stream moves at a perfectly constant three miles an hour.
Solution:
2
Ignore the speed of the stream, as the cork will be carried along at three miles per hour as will you. It takes two hours to travel fourteen miles, at a rate of seven miles per hour.
Comments (40)
Problem number 8 should be moved from the fact section to the fanciful section. It is a witty answer, albeit inaccurate from a factual perspective.
In 'The Bobber', the question states you can travel seven miles per hour through a placid lake, not six. Since the stream is moving three miles per hour and you are moving upstream, you are actually moving four miles per hour, not three. The answer is incorrect.
I have to disagree with you on #8. If you are traveling up stream at 7 miles an hour, in 2 hours you would reach the fisherman. You would meet the bobber sooner?
If you take over the person in front, you become 3rd because the person in front was 3rd.
Hi,
Shouldn't the question number 8 be that the fisherman looses his bobber downstream from you. Otherwise if you are down stream to the fisherman and are travelling downstream still at a speed of 17 miles an hour(3 mph by the stream and 14 mph on your own), you will never be able to catch the bobber and the distance will keep increasing.
The question number 8 should clarify that the fisherman loses his bobber downstream. If you are downstream and traveling at a speed of 17 miles an hour, you will never catch the bobber as the distance will keep increasing.
The problem concerning the bobber has the wrong solution. The boat travels upstream, therefore the speed of the stream should be subtracted.
The solution to the bobber problem is incorrect. The boat travels upstream, so the speed of the stream should be subtracted from the boat's speed.
In The Bobber puzzle, the direction should be changed from upstream to downstream.
The answer is in error. The speed of the stream is relevant because rather than meet at the 14 mile marker, you only travel 8 miles.
The answer to The Bobber puzzle is incorrect. The speed of the stream affects the distance traveled, meaning you only travel 8 miles instead of the assumed 14 mile marker.
Your answer fails to take into account the 3 miles per hour you lose due to traveling upstream.
If you are traveling upstream you are going against the current.
If you are traveling upstream at 7 miles an hour, in 2 hours you would reach the fisherman. You would meet the bobber sooner.
Your solution is incorrect. If you were sitting in the stream, the bobber would indeed be carried at the same speed, but the problem is you are traveling upstream, therefore against the current.
The solution to the bobber puzzle is incorrect. If you are paddling upstream against a -3 miles per hour current, you would only travel at 4 miles per hour. The bobber would travel at 3 miles per hour, making it 11 miles from the starting point in one hour.
Your chart was a clever idea, but it doesn't quite fit the situation regarding the probabilities of children being boys born on Tuesday.
The question should specify the probability of two boys born on Tuesday instead of any day.
I think you should change the wording to downstream, since you seem to be implying that the river is carrying you and the bobber; upstream would be against the current.
I need a better explanation for puzzle #8. I believe number 7 is incorrect.
Puzzle Number 8 should be in the 'very easy' category and not 'easy'. I solved it in 10 seconds and was looking for some sort of trick to it but there was none.
I don't think number 8 is possible because I have never seen any yachts in the Dead Sea. They don't work for the same reason the man didn't drown.
I believe that the given answer for number 8 is incorrect. If the bird is flying between the boys, and the boys are moving closer to each other as time moves, then it would greatly shorten the distance the bird flies.
The explanation for 'The Bobber' is incorrect. The speed of the stream should be considered, as it affects the time it takes for the bobber to meet the canoe.
The posted solution to puzzle #8 is misleading. The advice to 'ignore the speed of the stream' is incorrect, as it is essential to arrive at the closing rate of 7 MPH.
The solution to puzzle #8 in the Very Easy Logical Problems is misleading. While the answer is correct, the advice to ignore the speed of the stream is incorrect, as it is essential for calculating the closing rate.
Question 8 is wrong. The friend gets closer together as the bike gets longer. The first trip is 27 miles long.
Puzzle 8 could have been on a river. Some solutions seem fact-based rather than thought-out. For example, in puzzle 3, there could be other reasons like a tax or tip affecting the outcome.
For logic puzzle 8, the answer should be 50% instead of 13/27 due to the wording of the question regarding the probability of having another boy.
The answer for this question is wrong because it doesn't take into account the fact that the bobber is moving downstream while you are paddling upstream.
This cannot have an answer of 2 because the bobber is moving downstream while you are paddling upstream.
Your answer is incorrect. Water flows downstream, not upstream. Therefore, you are paddling against the current and the bobber is flowing away from you at the speed of the current.
The answer to 'The Bobber' is incorrect. Water flows downstream, not upstream, meaning you are paddling against the current and the bobber is flowing away from you at the speed of the current.
I just can't seem to comprehend the whole canoe/bobber problem. Yes the bobber will travel downstream at 3mph. However, the speed you can travel on a placid lake while paddling is not the speed you can depend on while you are traveling upstream against a current. For this problem, we'll presume you can maintain 7mph. So, the bobber is traveling downstream and you are traveling up, and you begin 12 miles apart, shouldn't they meet in 1 hr and 12 minutes? 3 * t + 7 * t = 12miles (3 +7) * t = 10 * t t = 12/10 or 1 and 2/10 (1/10 hr = 6 min)
I just can't seem to comprehend the whole canoe/bobber problem. The speed you can travel on a placid lake while paddling is not the speed you can depend on while you are traveling upstream against a current.
my bad on bobber question, still confused (3 +7) * t =14 10 *t = 14 t = 14/10 or 1 and 4/10 or 1 hr and 24 min
The question regarding the two boys is simply about the probability that the second child is a boy. The phrasing implies that the sex of the first child does not influence the sex of the second, as they are independent events.
The correct term is 'loses', not 'looses'.
Shouldn't the question state that the fisherman loses his bobber downstream from you? Otherwise, if you are downstream from the fisherman and traveling downstream, you will never be able to catch the bobber.
The question states you can travel seven miles per hour through a placid lake. Then it says the stream is moving three miles per hour, and you are moving upstream. That means you are moving four miles per hour, not three. The answer is wrong.
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