Gifted Issues Discussion homepage Forums General Discussion The Ultimate Bad Homework Question Thread!

Actually seems to me he is ramping is schedule each week.

So first week for each of the seven days he his jogging 2 miles
2nd week each day he jogs 3.5
3rd is 5
4th is 6.5
and 5th is 8

y = x*1.5 + 2

edited to say: funny how start typing something and get distracted submit and there are three or four responses in between

Also, I'd say that finding the Y intercept in this question is pretty strange, because in this case, X can only be a positive integer.

It would make sense for this problem that the Y intercept is when X = 0, because he's not running yet. But if you try to graph the following values, you'll see that the result is not a linear equation:

X | Y
-------
0 | 0
1 | 2
2 | 3.5
3 | 5
4 | 6.5
5 | 8

I would be shocked if the answer were not Y = 1.5X + 2. The y-intercept has to be 2 if you want to model the situation as a linear relationship. Because of the wording in the first sentence of the problem, I just assumed that the increase is 1.5 miles each week even though he jogs every day.

I think that it's great that your DD is giving it so much thought and considering all the possibilities - it's the hallmark of a strong mathematical mind.

I also think that once your DD receive more exposure to how many problems in science/social studies are modeled with the x-axis representing time but X=0 not the beginnng of time, it will make more sense. I guess I have always found it helpful to think of X=0 as the point before the change since the slope is meant to model the rate of change. For example, X=0 can be the year 1945 if you are plotting economic data regarding the increase in housing construction post WWII.

Sigh. Just looked at DS's science test on physical vs chemical changes. There were 15 questions, he had 5 marked as incorrect. Here is the first:

Intro: Read about each physical or chemical change in matter. Answer each question.
1. You crumple a paper bag into a ball.
What change happened? DS answered physical. INCORRECT
Is the bag still a bag? YES
Is this a physical or chemical change? DS answered physical. CORRECT

Why is the first answer incorrect and the third correct? Because he was supposed to infer, apparently, what the teacher meant to ask (describe what the paper bag looks like now, or something like that) rather than what she actually asked, which he correctly answered. He missed two more for exactly the same reasons.
It gets better. The other two he missed had to do with the second question in the series, like this.
A metal toy is left in a puddle of water and it rusts.
Is the metal still a metal? He said yes. INCORRECT
Is this a physical or a chemical change? He said chemical. CORRECT
So he knows that rusting is a chemical change, but (and I haven't had the energy to ask him about this yet) my guess is that he answered yes to the other question because he is picturing a toy that has not completely turned to rust and therefore the metal part that remains is still metal. I find the question as written to be rather nonsensical and confusing.

Now I am again in a dilemma about whether to discuss this with the teacher or not. It is 3rd grade so I am not overly concerned about the grade itself, but I AM concerned about how DS is supposed to figure out when he is answering questions correctly or incorrectly when it appears to be quite arbitrary in many instances.

For me, the larger problem with questions like the ones you described are that they encourage muddled thinking and require that kids make unjustified assumptions. If a question is much worse than the usual bad ones, I might bring it to the teacher's attention, but my usual tactic is to go over the flaws in the question and teach my kids how to recognize them.

Last night DD had a probability question: There were five numbers in a bag (0-4), and three were picked and not replaced. Zero wasn't picked. What was the probability of picking a 2 on the next turn?

DD was flustered because she'd removed the 2 in our mockup of the problem. But she wasn't sure what to think. "Should I put back the 2???" I explained that it was a bad question and asked her to think about different possible scenarios. She ended up understanding that because the question didn't specify whether or not the 2 had been picked, there were two possible scenarios: it had been picked, and the probability was therefore zero, or it hadn't, and the probability was therefore
one-half.

I hope that these lessons will ultimately do her a lot of good by teaching her to recognize bogosity. I don't know if I've helped you; it's really not an easy question.

I think the key point is that it is 3rd grade. We have found that teachers in elementary school often do not know the correct answers. Perhaps they once knew and have forgotten. Or perhaps they were just sloppy about forming the questions.

Much earlier on this thread I shared examples from our son's 4th grade teacher: "The sun doesn't move, or rotate", and "Q: Isn't a circle made up of an infinite number of points? A: It depends how big the circle is".

Given that it is elementary school, and that the teachers are not specialized, I would say to let it go. Our approach was to tell our son that he was right, and that not everything that is wrong is worth correcting in a discussion or argument. On the other hand, if this was in high school, where the stakes are higher, it might be a different matter.

Interesting, my take is I have a 50% chance of getting the known: 0. And a 50% chance of picking the unknown, and the unknown has a 25% chance of being 2. So .5 X .25 = 12.5% of picking 2. If that is the answer they want, it's a good problem.

You can get at it from the pick/not picked approach. Then you have to calculate the given x selections the probability of not picking a particular. Set aside 0. First pick 3/4 of not being 2. Second is 2/3 chance of not. Third is 1/2 chance of not. 1/2 * 3/4 * 2/3 = 1/4 (the same as simply picking 2 as the excluded number pick.)

So 25% of the time it's not picked. In that scenario, you have a 50% chance of picking 2. Which is 12.5%.
As noted the not picked case is 0%. So the total probability is still 12.5%.

Thanks val and mithawk, honestly I would prefer NOT to bring it up to the teacher because the last time I said something she did not react well (see my earlier posts about the categorization of the word stranger as something someone does).

My concern is that, although no grade was put on the test, he is a perfectionist and internalizes these grades as his own failure ("I'm bad at science"). We are working on this separately, but incidents like this don't help at all.

I think I have been avoiding undermining the teacher's authority by telling him that the questions are poorly written and that he is in fact correct. But I guess I am going to have to do that, though, in order for him to feel secure in his own abilities, which is ultimately more important.

It was a fourth grade math problem. So they meant "2" literally and weren't interested in what you might call subtleties. Though personally, I like your insight.

I see this point; it's important, because you (well, me too) don't want to give the child the impression that it's okay to be disrespectful of the teacher. I let my daughter write corrects answers (e.g. as in the probability problem), but I also tell her that it's only a few problems out of dozens and that not every teacher can catch every mistake. Maybe we even missed one and just barreled through it! I think there are ways to address it carefully. I had this same conversation with my older son last year. He's much more likely to be brusque, but he got the idea, too.