Since I present quizzes several times a year you can imagine how nervous I was when I received an e-mail that started "
Okay Doug...got one for you." Now I do get quizzes from time to time from members of the readership but this is the first one from a participant with a nearly perfect score on all the quizzes over the years - an extremely smart man whom I admire.
After working the problem I was quite relieved when I received his passing grade "Yes that's correct.
Well done, Doug."Below is the subject quiz that I added a Part B to since that is the way I worked the problem.
Please let me know how you work the problem. I will post all correct answers or alternatively will send the solution privately to anyone who requests it if no one figures it out.
Two Men & A Dog Quiz
Two men are walking toward each other, one is walking at 10 miles an hour the other is walking at 5 miles an hour. They meet after one hour. A dog is running back and forth between them at 8 miles an hour immediately turning around each time he gets to one of the men, until the men meet. A) How many miles did the dog run? & B) Where is the dog when the two men meet if the dog starts with the man who walks @ 5 miles per hour?
I think you like sending me these to see how my convoluted answers end up. It ain't purty, but I think its close.
ReplyDeleteWhat I did was breakdown everything into yards. They all start 15 miles apart (26400 yards)
Adding the dog's rate and the fast walker, it would take 50 minutes to cover the distance. The dog covers 11,735 yards.
The dog is slower than the fast man's pace and immediately falls behind. The fast man needs 10 minutes to cover the remaining 2933 yards.
It will take the dog 12.5 minutes to cover that distance. Total distance covered by the dog is 14,668 yards or 8.33 miles
You are all around it but answered the wrong question. What you did was correct as far as it went. Please look again. They don’t all have to meet – just the two men. So how many miles did the dog run wherever he is & how far is the dog from the men when the men meet? Remember the dog starts with the slower man.
DeleteWhen the 2 men meet, after one hour, the dog would have traveled 8 miles. (At 8 miles per hour, duh).
DeleteThe dog would be 1/3 mile away from where the 2 men meet.
That's more like it. Way to go.
DeleteJerry gave up. I was dizzy before I started.
ReplyDeleteTook the boys 1 minute to figure 8 miles and the dog where the men meet that is, in between them!
ReplyDeleteThe boys got Part A correct. Don't understand where the dog is - he is not between the men. Please explain.
DeleteMy rationale is that if the dog runs back and forth between the two men, it will always be in the space between them. Therefore, when the two men meet, the space in between them is essentially nothing, so the dog must be in between the two men. I understand a specific answer can be found, but logically speaking, I find that the dog would simply be located between the two men.
DeleteFrom Sam & Michael
Would be true except the fast man walks faster than the dog runs.
DeleteThe two men meet in one hour so they are 15 miles apart if one walks 10 MPH & the other 5 MPH. The answer to Part A is found right there – if the dog runs 8 MPH he runs 8 miles within the definition of the problem.
ReplyDeleteThe fast man & the dog are moving @ a combined 18 MPH speed so they travel the 15 miles & meet in less than 1 hour – 15/18 of an hour or 50 minutes.
The fast man is traveling 1.25 times faster than the dog (i.e., 10/8). The fast man will have walked 8 1/3 miles (15/18 X 10) & the dog will have run 6 2/3 miles (15/18 X 8) when they meet. The fast man will be travelling faster than the dog runs when the dog turns around to run toward the slow man.
The fast man has 1 2/3 miles to walk (10 – 8 1/3) & the slower man 5/6 miles (i.e., 15/18) to walk before they meet. This works out to 1/6 hours (i.e., 10 minutes) before they meet: 1 2/3 miles/10 mph = 0.167 hours; check 5/6 miles/5 mph = .167 hours
In 0.167 hours the dog will have run 1 1/3 miles & will be 1/3 miles away from the two men when they meet (i.e., 1 2/3 – 1 1/3 = 1/3)
The dog will have run 8 miles total (6 2/3 +1 1/3 = 8)
With re to Part A – both men & the dog all traveled the distance given in the statement of the problem – i.e., MPH X 1 hour = miles. Ten & five miles respectively for the two men & eight miles for the pooch.
Doug - I just realized that I didn't send the solution to the quiz listed below.
ReplyDeleteHere it is.
a ) the 2 men meet in an hour,and during that time the dog has covered a distance of 8 miles running back and forth between the 2 men , since that is the speed of the dog ( 8 mph)
b) Since the dog is running between the 2 men back and forth as the 2 men approach each other the distance between them gets shorter, until the dog meets the 2 men when they meet, in other words the 3 of them meet at the same instant.
I wondered what happened to your answer to this quiz. You have Part A correct – once it is determined that the time is one hour the problem actually states how far the dog runs – 8 miles. No more to Part A than that. With regard to Part B please try again realizing that the faster man walks faster than the dog runs so the dog is behind the faster man running toward the two men who actually meet but without the dog being with them.
DeleteDoug - Using GPS (joking), the location where the dog is when the 2 men meet is either 10 miles from the start of the walk by the 1st man or 5 miles from the start by the 2nd.
DeleteThe dog starts with the slower man so the dog pulls away from him from the get go. The faster man is walking toward the dog @ 10 mph & the dog is running @ 8 mph toward the faster man so they will meet before the two men meet. When the dog turns around to run toward the slower man the faster man pulls away from the dog. Take it from there.
DeleteThe dog meets the man walking at 10 mph, when it has run 6.6 miles, and the man walking towards him has covered 8.4 miles. Now, the dog turns around and the man continues towards the other man, and when they both meet, the dog is 5.4 miles away from his starting point.
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