[ARCHIVED THREAD] - MPH Question (Page 1 of 2)
Posted: 3/19/2010 6:09:56 AM EDT
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This question was given to me in a recent class. I don't know how to do a poll.
I drove from home to work at an average speed of 60 MPH. I then drove from work to home at an average speed of 30 MPH. What was my average speed for the entire trip. A) 40 MPH B) 45 MPH C) 50 MPH D) How Should I know? |
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Quoted: No idea...did you take the same route?This question was given to me in a recent class. I don't know how to do a poll. I drove from home to work at an average speed of 60 MPH. I then drove from work to home at an average speed of 30 MPH. What was my average speed for the entire trip. A) 40 MPH B) 45 MPH C) 50 MPH D) How Should I know? |
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Quoted: This question was given to me in a recent class. I don't know how to do a poll. I drove from home to work at an average speed of 60 MPH. I then drove from work to home at an average speed of 30 MPH. What was my average speed for the entire trip. A) 40 MPH B) 45 MPH C) 50 MPH D) How Should I know?   |
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Does entire trip mean from when you leave your house to when you get back to your house? It depends on the distance to work and how long you were at work. Average speed = total distance / total time. They're ignoring time spent at work. Just time traveling. |
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Quoted: A is the correct answer. If your distance to work is 30 miles, then you spend 1/2 hour at 60mph going to work and 1 hour at 30 mph going home. That's 60 miles in 90 minutes. Or 40 miles per hour. The ratio stays the same regardless of the distance. While technically correct, there is no time implication in the question itself. Since time is of no consequence to the way the question was written, 45 MPH is correct. |
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A is the correct answer. If your distance to work is 30 miles, then you spend 1/2 hour at 60mph going to work and 1 hour at 30 mph going home. That's 60 miles in 90 minutes. Or 40 miles per hour. The ratio stays the same regardless of the distance. While technically correct, there is no time implication in the question itself. Since time is of no consequence to the way the question was written, 45 MPH is correct. and we're off! Canadian school system fail? More facepalm! |
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60 MPH/X + 30 MPH/X = 90 MPH/2X = 45 MPH/X Where X = Distance from home to work and vice versa. Not quite. The correct way would be to calculate your total time for driving both trips (Distance/Speed). Then you would divide the total distance (Length of drivng to work + home from work) by the total time previously calculated. Answer ends up being 40MPH ETA: Beaten to it 
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A is the correct answer. If your distance to work is 30 miles, then you spend 1/2 hour at 60mph going to work and 1 hour at 30 mph going home. That's 60 miles in 90 minutes. Or 40 miles per hour. The ratio stays the same regardless of the distance. While technically correct, there is no time implication in the question itself. Since time is of no consequence to the way the question was written, 45 MPH is correct. Average speed is defined as distance / time. Time is implicated and is of consequence. |
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Quoted: Quoted: A is the correct answer. If your distance to work is 30 miles, then you spend 1/2 hour at 60mph going to work and 1 hour at 30 mph going home. That's 60 miles in 90 minutes. Or 40 miles per hour. The ratio stays the same regardless of the distance. While technically correct, there is no time implication in the question itself. Since time is of no consequence to the way the question was written, 45 MPH is correct. I disagree. MPH does include a time factor, H=Hour. An average speed also includes this time factor and is required for an answer. |
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Quoted: I know, I realized that shortly after seeing the other posts below.Quoted: 60 MPH/X + 30 MPH/X = 90 MPH/2X = 45 MPH/X Where X = Distance from home to work and vice versa. Not quite. The correct way would be to calculate your total time for driving both trips (Distance/Speed). Then you would divide the total distance (Length of drivng to work + home from work) by the total time previously calculated. Answer ends up being 40MPH ETA: Beaten to it I was trying to add the time into the equation but didn't do it right in my sleep deprived state. Didn't do what my mathematics professor always told us to do. "Think about your answers logically. Do they make sense?" Didn't check to see if it made sesne. |
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Time isn't stated at all in the question, just average speed.
This is one of those questions teachers throw out there to fuck with people. They know some people will over complicate it and get one answer, while simpletons like me will do a quick average and get a different answer. |
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Quoted: Quoted:and we're off! Canadian school system fail? More facepalm! What was my average speed for the entire trip. Right.... Did you notice how the question was worded? Obviously not, that's okay, let me spoon feed it to you. Time is not of consequence because it says "what was the total time of the trip". So, exactly how much time was spent at work? We don't know, because it doesn't tell us, therefore, time is not of consequence. It could have been 4 hours, or 8 or 16 or 4.52. We don't know. Before we can calculate the AVERAGE SPEED from a-b-a, we need the TOTAL TIME, which we don't have. |
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I thouht it was a little flawed but he said the answer is A. His explanation was 60 MPH = 1 Hour. Same distance at 30 MPH = 2 Hours. 60 + 30 + 30 = 120 / 3 = 40 MPH This doesn't make sense to me, why does 60mph have to = 1 hour? Just because the vehicles average speed is 60mph doesnt mean it took him an hour to get to the destination. But hey im not a mathematician
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and we're off! Canadian school system fail? More facepalm! What was my average speed for the entire trip. Right.... Did you notice how the question was worded? Obviously not, that's okay, let me spoon feed it to you. Time is not of consequence because it says "what was the total time of the trip". So, exactly how much time was spent at work? We don't know, because it doesn't tell us, therefore, time is not of consequence. It could have been 4 hours, or 8 or 16 or 4.52. We don't know. Before we can calculate the AVERAGE SPEED from a-b-a, we need the TOTAL TIME, which we don't have. I agree. It does say how long he was at work or how long his lunch break is. Or what he had for lunch? Was it taco tuesday? There is just not enough info. Thanks for chiming in Canada, but stick with the hockey questions. I say A = 40mph for all the reasons listed above. |
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I thouht it was a little flawed but he said the answer is A. His explanation was 60 MPH = 1 Hour. Same distance at 30 MPH = 2 Hours. 60 + 30 + 30 = 120 / 3 = 40 MPH This doesn't make sense to me, why does 60mph have to = 1 hour? Just because the vehicles average speed is 60mph doesnt mean it took him an hour to get to the destination. But hey im not a mathematician 60 mph for 2 hours and same distance at 30mph at 4 hours. 60 + 60 +30 +30+30+30 = 240/6 = 40 mph. it doesn't have to be 1 hour. plug any number in. If you drove for an hour at 60 mph and then drove for an hour at 30 the average would be 45mph but the person would have only made it half way home which isn't what the question was asking. |
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Quoted: Quoted: Quoted: Quoted:and we're off! Canadian school system fail? More facepalm! What was my average speed for the entire trip. Right.... Did you notice how the question was worded? Obviously not, that's okay, let me spoon feed it to you. Time is not of consequence because it says "what was the total time of the trip". So, exactly how much time was spent at work? We don't know, because it doesn't tell us, therefore, time is not of consequence. It could have been 4 hours, or 8 or 16 or 4.52. We don't know. Before we can calculate the AVERAGE SPEED from a-b-a, we need the TOTAL TIME, which we don't have. I agree. It does say how long he was at work or how long his lunch break is. Or what he had for lunch? Was it taco tuesday? There is just not enough info. Thanks for chiming in Canada, but stick with the hockey questions. I say A = 40mph for all the reasons listed above. LOL. You voted for Obongo, didn't you? |
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and we're off! Canadian school system fail? More facepalm! What was my average speed for the entire trip. Right.... Did you notice how the question was worded? Obviously not, that's okay, let me spoon feed it to you. This isn't going to end how you think. Hope you have your bib ready. Time is not of consequence because it says "what was the total time of the trip". So, exactly how much time was spent at work? We don't know, because it doesn't tell us, therefore, time is not of consequence. It could have been 4 hours, or 8 or 16 or 4.52. We don't know. Time is always "of consequence" when you're discussing a rate. That said, it actually says "What was my average speed for the entire trip", not what you said in the quote here. Before we can calculate the AVERAGE SPEED from a-b-a, we need the TOTAL TIME, which we don't have. No, you don't. You have rates, those are all you need to calculate a derived rate. So settle in, because now I'll spoon feed it to you, punkin. If he went half speed going home, then it took him twice as long to get home, no matter the distance or wall clock time. This means he was going 30mph twice as long as he was going 60. So if you go 30mph for 4 hours and 60 for 2, what is your average speed? What if you go 30 mph for 400 hours and 60 for 200? What about 30 for 4,000,000 and 60 for 2,000,000? Oops. They all come out the same. So, the average speed = (speed-to-work + (2 * speed-from-work)) / 3 = (60 + (2 * 30)) /3 = (60 + 60) / 3 = 120 / 3 = 40 Here, lemme wipe that off your chin. |
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and we're off! Canadian school system fail? More facepalm! What was my average speed for the entire trip. Right.... Did you notice how the question was worded? Obviously not, that's okay, let me spoon feed it to you. Time is not of consequence because it says "what was the total time of the trip". So, exactly how much time was spent at work? We don't know, because it doesn't tell us, therefore, time is not of consequence. It could have been 4 hours, or 8 or 16 or 4.52. We don't know. Before we can calculate the AVERAGE SPEED from a-b-a, we need the TOTAL TIME, which we don't have. I agree. It does say how long he was at work or how long his lunch break is. Or what he had for lunch? Was it taco tuesday? There is just not enough info. Thanks for chiming in Canada, but stick with the hockey questions. I say A = 40mph for all the reasons listed above. LOL. You voted for Obongo, didn't you? Here try this one A slap shot travels from one end of the rink to the other at 60 MPH. Then Claude goes to the other end and shots the puck back at 30 MPH. What was my average speed of the trip of the puck. A) 40 MPH B) 45 MPH C) 50 MPH D) How Should I know? |
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Quoted: Quoted: Quoted: Quoted:and we're off! Canadian school system fail? More facepalm! What was my average speed for the entire trip. Right.... Did you notice how the question was worded? Obviously not, that's okay, let me spoon feed it to you. This isn't going to end how you think. Hope you have your bib ready. Time is not of consequence because it says "what was the total time of the trip". So, exactly how much time was spent at work? We don't know, because it doesn't tell us, therefore, time is not of consequence. It could have been 4 hours, or 8 or 16 or 4.52. We don't know. Time is always "of consequence" when you're discussing a rate. That said, it actually says "What was my average speed for the entire trip", not what you said in the quote here. Before we can calculate the AVERAGE SPEED from a-b-a, we need the TOTAL TIME, which we don't have. No, you don't. You have rates, those are all you need to calculate a derived rate. So settle in, because now I'll spoon feed it to you, punkin. If he went half speed going home, then it took him twice as long to get home, no matter the distance or wall clock time. This means he was going 30mph twice as long as he was going 60. So if you go 30mph for 4 hours and 60 for 2, what is your average speed? What if you go 30 mph for 400 hours and 60 for 200? What about 30 for 4,000,000 and 60 for 2,000,000? Oops. They all come out the same. So, the average speed = (speed-to-work + (2 * speed-from-work)) / 3 = (60 + (2 * 30)) /3 = (60 + 60) / 3 = 120 / 3 = 40 Here, lemme wipe that off your chin. Oh. My. Fucking. God. Do you understand what the term TOTAL means? ETA - I just checked. YOU DON'T. |
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I thouht it was a little flawed but he said the answer is A. His explanation was 60 MPH = 1 Hour. Same distance at 30 MPH = 2 Hours. 60 + 30 + 30 = 120 / 3 = 40 MPH This doesn't make sense to me, why does 60mph have to = 1 hour? Just because the vehicles average speed is 60mph doesnt mean it took him an hour to get to the destination. But hey im not a mathematician 60 mph for 2 hours and same distance at 30mph at 4 hours. 60 + 60 +30 +30+30+30 = 240/6 = 40 mph. it doesn't have to be 1 hour. plug any number in. If you drove for an hour at 60 mph and then drove for an hour at 30 the average would be 45mph but the person would have only made it half way home which isn't what the question was asking. Hmm makes sense, thanks for explaining. I always miss something in word problems, at first glance i didnt even think of home/work work/home being same distance but this makes sense now. |
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Quoted: Quoted: Quoted: Quoted: Quoted:and we're off! Canadian school system fail? More facepalm! What was my average speed for the entire trip. Right.... Did you notice how the question was worded? Obviously not, that's okay, let me spoon feed it to you. This isn't going to end how you think. Hope you have your bib ready. Time is not of consequence because it says "what was the total time of the trip". So, exactly how much time was spent at work? We don't know, because it doesn't tell us, therefore, time is not of consequence. It could have been 4 hours, or 8 or 16 or 4.52. We don't know. Time is always "of consequence" when you're discussing a rate. That said, it actually says "What was my average speed for the entire trip", not what you said in the quote here. Before we can calculate the AVERAGE SPEED from a-b-a, we need the TOTAL TIME, which we don't have. No, you don't. You have rates, those are all you need to calculate a derived rate. So settle in, because now I'll spoon feed it to you, punkin. If he went half speed going home, then it took him twice as long to get home, no matter the distance or wall clock time. This means he was going 30mph twice as long as he was going 60. So if you go 30mph for 4 hours and 60 for 2, what is your average speed? What if you go 30 mph for 400 hours and 60 for 200? What about 30 for 4,000,000 and 60 for 2,000,000? Oops. They all come out the same. So, the average speed = (speed-to-work + (2 * speed-from-work)) / 3 = (60 + (2 * 30)) /3 = (60 + 60) / 3 = 120 / 3 = 40 Here, lemme wipe that off your chin. Oh. My. Fucking. God. Do you understand what the term TOTAL means? ETA - I just checked. YOU DON'T. You are interjecting something into the problem that doesn't exist. I don't see anywhere in the question that says that the person didn't pull into the parking lot of their job, and forgot their wallet, so they turned right around and went back, or that the office was closed, or it was actually Saturday, etc. The only information you are given is the rate at which the person travels. There is nothing about working all day, or any of that other bullshit. |
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Oh. My. Fucking. God. Do you understand what the term TOTAL means? ETA - I just checked. YOU DON'T. Could you point out where the OPs question has that word in it? I can't find it. You are embarrassing yourself and your country. Cool story, bro. Wow, you're pretty sad. Take a deep breath, read the question and the answers again, man up, and admit you are wrong. |
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Quoted: We know that the the time spent at 60MPH is half that spent at 30MPH, since this distance traveled is the same. Call time at 60MPH "t" then the time at thirty is 2t. total distance traveled is 60t plus 30*2t = 120t. the average speed is the distance divided by time = (120t)/(3t) =40MPH.Quoted: Quoted:and we're off! Canadian school system fail? More facepalm! What was my average speed for the entire trip. Right.... Did you notice how the question was worded? Obviously not, that's okay, let me spoon feed it to you. Time is not of consequence because it says "what was the total time of the trip". So, exactly how much time was spent at work? We don't know, because it doesn't tell us, therefore, time is not of consequence. It could have been 4 hours, or 8 or 16 or 4.52. We don't know. Before we can calculate the AVERAGE SPEED from a-b-a, we need the TOTAL TIME, which we don't have. |
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Quoted: Quoted: Quoted: Quoted: Oh. My. Fucking. God. Do you understand what the term TOTAL means? ETA - I just checked. YOU DON'T. Could you point out where the OPs question has that word in it? I can't find it. You are embarrassing yourself and your country. Cool story, bro. Wow, you're pretty sad. Take a deep breath, read the question and the answers again, man up, and admit you are wrong. The question implies that time was spent at work. I see that and you don't. |
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The question implies that time was spent at work. I see that and you don't. Are you fucking kidding? Here is the question again: "I drove from home to work at an average speed of 60 MPH. I then drove from work to home at an average speed of 30 MPH. What was my average speed for the entire trip. " If the question implies anything it's that the guy turned right the fuck around and came back home without ever actually working. |
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Oh. My. Fucking. God. Do you understand what the term TOTAL means? ETA - I just checked. YOU DON'T. Could you point out where the OPs question has that word in it? I can't find it. You are embarrassing yourself and your country. Cool story, bro. Wow, you're pretty sad. Take a deep breath, read the question and the answers again, man up, and admit you are wrong. The question implies that time was spent at work. I see that and you don't. oh I get it now, you're a troll. Sorry |
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Quoted: Quoted: The question implies that time was spent at work. I see that and you don't. Are you fucking kidding? Here is the question again: "I drove from home to work at an average speed of 60 MPH. I then drove from work to home at an average speed of 30 MPH. What was my average speed for the entire trip. " If the question implies anything it's that the guy turned right the fuck around and came back home without ever actually working. Have I enraged you? Ruh-Roh. |
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Oh. My. Fucking. God. Do you understand what the term TOTAL means? ETA - I just checked. YOU DON'T. Could you point out where the OPs question has that word in it? I can't find it. You are embarrassing yourself and your country. Cool story, bro. Wow, you're pretty sad. Take a deep breath, read the question and the answers again, man up, and admit you are wrong. The question implies that time was spent at work. I see that and you don't. oh I get it now, you're a troll. Sorry You're probably right, my mistake for feeding it. 
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