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Post by Nikudou Natsumi on Dec 14, 2014 3:05:21 GMT
Okay, so we (Mikau, dogfish, ichthyophobia, and anyone else that joined in that I don't remember at the moment) were talking about math problems in the chat box and eventually ended up solving two distance-rate-time problems having to do with running/cycling and two people driving toward each other. So, just in case anyone wants to work on another, here's a third:
Page 141 #2 (for me to remember when I need to look at the answer)
Bill drove from Ajax to Bixby at an average speed of 50 mi/h. On the way back, he drove at 60 mi/h. The total trip took 4 2/5 h of driving time. Find the distance between these two cities.
Ganbare yo!
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Post by ichthyophobia on Dec 14, 2014 3:35:23 GMT
I drew like six graphs before I realized I could just take the average of the speeds. 121 miles.
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Post by Nikudou Natsumi on Dec 14, 2014 3:40:03 GMT
Close? Question: was your answer rounded?
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Post by StarlightDragons on Dec 14, 2014 3:41:30 GMT
2.4 miles? nope jk I messed something up XD
and then I got 12.5, and then I realized I totally misread the question. sigh. this is why you need sleep, people! XD
Okay, I just did the wrong operation. I divided when i should've multiplied. Wow. I got 121 miles as well. sleep. I will sleep eventually.
Process: (50+60)/2 = 55 mph (average, because the distances are the same) d=rt: 2d=(55mph)(4.4hr) 2d=242 d=121
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Post by Nikudou Natsumi on Dec 14, 2014 4:22:31 GMT
The answer key claims it is 120 miles. I shall now go to check whether I misread that or not. And no, apparently I didn't. Hmmm . . .
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Post by StarlightDragons on Dec 14, 2014 4:59:06 GMT
Sudden thought right before I actually fall asleep- maybe it rounded sig figs?
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Post by ichthyophobia on Dec 14, 2014 5:01:51 GMT
that'd explain it, though I've never seen anyone care about sig figs outside of a science class.
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Post by Nikudou Natsumi on Dec 14, 2014 5:02:28 GMT
I don't think it'd do that though . . . There was nothing about rounding on the problem itself, and it didn't round on anything else, even going into the decimals, so . . . Well, it rounded once it got into a certain point in the decimals, but what I was trying to say was just the fact that it went into decimals.
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dogfish44
Junior Member
You are now aware that you are breathing manually!
Posts: 99
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Post by dogfish44 on Dec 14, 2014 17:28:19 GMT
Averages don't quite work - lemme demonstrate. {Spoiler: Click to view/hide}Let's say the distance from A to B is 60 Miles. At 20 Miles Per Hour, that would take 3 hours. At 30 Miles Per Hour, that would take 2 hours.
Let's now say I go from A to B at 20 Miles Per Hour, then I go from B to A at 30 Miles Per Hour.
The total time taken is 5 hours. The distance travelled is 120 Miles. This gives me an average speed of 24 Miles Per Hour. If we were to assume an average of 20 and 30, we'd be looking for 25 Miles Per Hour, which this is not. ------ As for this question... graph time {Spoiler}
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Post by StarlightDragons on Dec 14, 2014 17:34:31 GMT
ah, that makes much more sense! thank you!
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Post by Mikauzoran on Dec 14, 2014 17:36:42 GMT
I love your graphs, dogfish! They're so pretty, and they make sense! I don't think I could craft one of my own, but...
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Kaggami
Beta Reader
I´m freezing in my own house... winter, no one invited you yet!
Posts: 527
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Post by Kaggami on Dec 26, 2014 4:17:21 GMT
I don´t even know how to work with miles... XD I always use kilometers or meters
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Kaggami
Beta Reader
I´m freezing in my own house... winter, no one invited you yet!
Posts: 527
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Post by Kaggami on Dec 26, 2014 4:21:07 GMT
problem:
I have double of the age I had when my father had the age I have now. Furthermore, the addition of our ages is 100. What is our age?
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Post by StarlightDragons on Dec 26, 2014 4:47:53 GMT
... //attempts and fails// {fail mathwork} ...I'm 40 and my father's 60, maybe...? will put the work in later, it's on an art program atm XD
now it's up:
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Post by Nikudou Natsumi on Dec 26, 2014 5:07:41 GMT
My guess: Me: 40 Father: 60 I would explain my math, but most of it was mental math and making my own image by putting my hands in front of me at different levels. Eh, I'll try explaining my reasoning anyway: {my reasoning} Basically what I thought was that if "my" father was the age "I" am now, and I'm twice the age that I was then, then my father would be x years older than me. Now, I'm 2x, and if my father's x years older than me, then he's 3x. 2x + 3x = 5x, and divide 5x by 100, x = 20. And since I'm 2x, I'm 40 and my dad is what's left over: 60.
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