A “simple” 3rd grade problem • Hacker News Board

Re: A “simple” 3rd grade problem

#51

Post by DanBC » Sat, May 04, 2013, 5:03 PM UTC

utopkara wrote: post #24

This is a classical question I ask to children (and I was asked as a child too). It was/is fun, because it is easier to answer if you haven't yet started arithmetic, or if you can manage to step outside the pressure of this new thing that you are being taught at school. How many cuts do you need to make in order to split a board into 2? How about 3? How about 4? In this case, the teacher has failed. But, everybody mu…

> But, everybody must have learned something out of this.

Let's hope the lesson learnt is not "math is too hard for me; I'm stupid; I don't understand this; I tried to ask my teacher but they're authoritarian and because I'm just a kid I don't know the socially acceptable way to ask this kind of stuff and the teacher got all defensive and punished me, and so I must never question anyone, even when I think I can show that I'm right and I think they've made a mistake".

Teaching is a hard job. Many parents don't support you at all. It's politicised (at least, in England it's very political). It's low status. So, I'm not really knocking the teacher. I do hope that after a chat the teacher gave the child better marks.

Re: A “simple” 3rd grade problem

#52

Post by driverdan » Sat, May 04, 2013, 5:05 PM UTC

I have to laugh at how much play this got at Stack Exchange and here. This is simple, scare quotes are unnecessary. The teacher made a mistake. They're not perfect, they make mistakes just like the rest of us. End of story.

Re: A “simple” 3rd grade problem

#53

Post by gizmo686 » Sat, May 04, 2013, 5:05 PM UTC

quacker wrote: post #31

bayesianhorse wrote: post #14

The problem at hand is "what are you supposed to do" vs the actual problem at hand. At first I had a difficulty seeing why 20 should be wrong, but then it dawned upon me: The teacher set out to create a word problem for a specific mathematic solution strategy. Students probably were inundated with this strategy for weeks before the test, so for them it is very clear what they were supposed to do.

Absolutely. The test was probably written by the person grading it to cover fraction/ratio problems. The question shown is a poor rewrite of something like, "If it takes 10 minutes to fill two buckets, how long does it take to fill three buckets?"

The format of the page looks like something out of a book, not something that the teacher made. My guess of what happened is that when the teacher went to solve the problem, she read it as the bucket problem.

Re: A “simple” 3rd grade problem

#54

Post by pbreit » Sat, May 04, 2013, 5:05 PM UTC

Only on HN would you find people trying to make the case that the question is ambiguous. What is the matter with you people?

Re: A “simple” 3rd grade problem

#55

Post by gizmo686 » Sat, May 04, 2013, 5:07 PM UTC

randlet wrote: post #30

jamessb wrote: post #17

Earlier quoted context omitted.

Well, Phil Karlton said that "There are only two hard things in Computer Science: cache invalidation and naming things". Some people list off-by-one errors as the third hardest thing.

I think the joke is: "There are only two hard things in Computer Science; cache invalidation, naming things and off by one errors".

Whats the joke? The hard things are:

0) cache invalidation

1) naming things

2) off by one errors

Looks like he counted right to me.

EDIT: fixed newlines

Re: A “simple” 3rd grade problem

#56

Post by rquantz » Sat, May 04, 2013, 5:07 PM UTC

quacker wrote: post #31

bayesianhorse wrote: post #14

The problem at hand is "what are you supposed to do" vs the actual problem at hand. At first I had a difficulty seeing why 20 should be wrong, but then it dawned upon me: The teacher set out to create a word problem for a specific mathematic solution strategy. Students probably were inundated with this strategy for weeks before the test, so for them it is very clear what they were supposed to do.

Absolutely. The test was probably written by the person grading it to cover fraction/ratio problems. The question shown is a poor rewrite of something like, "If it takes 10 minutes to fill two buckets, how long does it take to fill three buckets?"

Yes, the teacher was trying to teach fractions, the student was doing discrete math.

Re: A “simple” 3rd grade problem

#57

Post by gizmo686 » Sat, May 04, 2013, 5:07 PM UTC

randlet wrote: post #30

jamessb wrote: post #17

Earlier quoted context omitted.

Well, Phil Karlton said that "There are only two hard things in Computer Science: cache invalidation and naming things". Some people list off-by-one errors as the third hardest thing.

I think the joke is: "There are only two hard things in Computer Science; cache invalidation, naming things and off by one errors".

Whats the joke? The hard things are: 0) cache invalidation 1) naming things 2) off by one errors

Looks like he counted right to me.

Re: A “simple” 3rd grade problem

#58

Post by georgemcbay » Sat, May 04, 2013, 5:07 PM UTC

jay_m wrote: post #22

bbx wrote: post #4

It's more a logic question than a math one. The confusion spawns from the fact that the three numbers present in the question are 10, 2, and 3 (so the thought process would be 2 = 10 min so 1 = 5 min, thus 3 = 15 min). But 2 represents the final state, though requires only 1 action (cut). And the required answer (time spent) is related to the number of actions, not the final state. This reminds me of the water lily p…

That water lily problem is very neat, hadn't heard of it before.

I hadn't heard of the water lily problem either. The answer was completely obvious to me, but I don't think this was because I'm particularly intelligent or math savvy, but rather because I'm used to working in binary, which I think gives you a better intuitive sense of the concept of doubling.

Re: A “simple” 3rd grade problem

#59

Post by jdiez17 » Sat, May 04, 2013, 5:08 PM UTC

driverdan wrote: post #52

I have to laugh at how much play this got at Stack Exchange and here. This is simple, scare quotes are unnecessary. The teacher made a mistake. They're not perfect, they make mistakes just like the rest of us. End of story.

It's quite scary though, at least to me. From the scribbles the teacher made, it looks like they are being taught to deal with fractions in the most mechanical way possible.

Re: A “simple” 3rd grade problem

#60

Post by jdiez17 » Sat, May 04, 2013, 5:08 PM UTC

driverdan wrote: post #52

I have to laugh at how much play this got at Stack Exchange and here. This is simple, scare quotes are unnecessary. The teacher made a mistake. They're not perfect, they make mistakes just like the rest of us. End of story.

It's quite scary though, at least to me. From the scribbles the teacher made, it looks like they are being taught to deal with fractions in the most mechanical way possible.