Skip to content

What was the matter with Math B #13?

January 28, 2009 am31 6:53 am

It didn’t make sense. They wanted the kids to set up inverse variation, solve, get 256, move to the next question.

But the problem didn’t make sense!

Carol notices that the number of customers who visit her coffee shop varies inversely with the average daily temperature. Yesterday, the average temperature was 40 and she had 160 customers. If today’s average temperature is 25, how many customers should she expect?

(1) 100    (3) 256
(2) 145    (4)  1,000

They wanted 256. (40)(160) = (25)(256).

But look kiddies, you are right to jump through the hoops they set for you. That’s your job. But if you are smart, you will ask, as you fly through the air, “why?”

And on #13, there is a number, but no reason why. Inverse variation must be the wrong model for this problem. Think about it. How much data did she need to “notice” that relationship? Jeez, I hope you’d fail an economics exam or an earth science exam if you tried to use inverse variation as a model here. What happens in Chicago? (think about it, the temp regularly gets near 0). What happens when it rains? Day of week?

Oh, “average daily temperature” – what exactly does that mean? The average daily temperature in July…. oops. I think they meant the average temperature for that day… but we don’t take those averages… how would we calculate them? what would they mean? People want the high, want the low.

When something makes no sense, someone should say something.

8 Comments leave one →
  1. Anonymous permalink
    January 28, 2009 am31 7:08 am 7:08 am


  2. January 28, 2009 am31 8:53 am 8:53 am

    Ah. Yeah, that makes sense to me. I just had no idea what the whole question was when I asked in the earlier post.

  3. January 28, 2009 pm31 6:15 pm 6:15 pm

    There is also the little detail that if the temperature is below zero, she sells negative cups of coffee…does that mean her customers bring her coffee and she gives them money? I am tempted to use this question as a warm up in my trig class with the prompt “Explain why this question is completely absurd”.

  4. Anonymous permalink
    January 28, 2009 pm31 9:42 pm 9:42 pm

    when it says inversley u multiply the first 2 numbers and divide by the third so 40×160 and divide by 25 and u get 256 very easy

  5. January 29, 2009 am31 7:39 am 7:39 am

    Can’t you just hear the justification?

    “As every competent 10th grade Chemistry student can tell you, the Fahrenheit temperatures are interval numbers and would have to be converted to Rankine in order to reliably run numbers through any ratio equation like Charley Boyle’s Law or this particular one.

    You know Rankine, don’t you? Oh wait. You didn’t attend Chemistry during the Kennedy or Johnson administration, did you?

    Sheesh. Sorry, kids.”

    Though a particularly bright one might have thought to convert to Kelvin, assuming the temperatures were Celsius. But it would have taken an international student or an especially bright one to realize that 40oC is pretty bloody hot (104oF) for people drinking coffee, but I digress.

    The answer is obviously 500(160)=485X
    We’ll charitably round that to 165 customers.

    You are spot on here, Jonathon. Trying for the real-world is so unfair, stupid, and counter-productive.

    Still, I’d give good money to see any kid who managed to come up with that answer go to Albany and dope-slap the test administrators in an open hearing.

  6. YO MAMA permalink
    January 31, 2009 am31 8:54 am 8:54 am

    u guys r all idiots…the anser was so obviously 256 cuz wen they say inversely that means it is inversely equal to todays temp and number of people other wise they wouldnt give u that information. wow to whoever didnt realize that. for all of u who think im being mean its cuz i got a 100 so suck it. but honestly that was a pretty easy question. 33 was the hardest i have to say.


  1. Weak gravity and other Math B oddities « JD2718
  2. My favorite bad exam target: Math B (and a puzzle) « JD2718

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: