Maths homework

[Arnold Layne]

8 minutes ago, Fullerene said:

Maths lesson in North Korea.

Yesterday in defence of our great republic I captured X capitalist pigs and locked them away.  80% were blond and rest were redheads

Today in honour of our supreme leader, I valiantly captured yet more of these swines.  This time 76 had blond hair and 48 had red.  My patriotism knows no bounds.

Now my prisoners are 75% blond and 25% redhead.

So now the question , my dear comrades, is this.  How many of these verminous shits had I captured yesterday?

Long live the DPRK.  Long live our glorious leader.

Is it 340?

[sugna]

2 hours ago, Arnold Layne said:

My ten year old has this problem to solve

I have X roses. 80% are white, the rest are red. I add 76 white and 48 red. Now 75% are white. What is the value of X?

I have worked out the answer using a spreadsheet but he needs to show workings.

Any ideas?

At 10 years old, I think that iteration is probably what the question is leading in to. That and a bit of approximation, and narrowing down solutions. Just getting used to thinkng about how numbers work ,rather than speadsheeting or using algebra.

You can see that adding one-and-a-half-ish as many white as red, and well over a hundred in total, only shifts the proportion by a small amount. As an approximation, a surplus of 50% is only affecting the overall surplus by 5%, a factor of 10; so the original number is getting on for that sort of ratio w.r.t. the addition. So there are clearly many hundreds of roses there to start with.

The original batch divides by 5 (because of the 80%); and the original whites divide by 4 (same reason); and the new batch divides by 4, and the total divides by 4 (because of the 75%)*.

So... maybe try somewhere in the high hundreds, such as 800 and 1000, and take it from there.

* and the eventual total of whites divides by 3** (because of the 75%), and 4 (because new and old both divide by 4; and so on - there are often things that you can infer in order to make better approximations as you're going along, or even just to make a good initial guess.

** so the original number of whites has a remainder of 2 when dividing by 3***.*** I wouldn't expect a 10yo to reason all the way through these steps, and I'm willing to bet that I've got some of them wrong in trying to illustrate when I'm 5 minutes from sleep. But it's useful to talk some of the options through, at least.

[Guest Moomintroll]

The answer is 42.
It always is.
It is.

I see you have found your level.

[D.A.F.C]

Why not just count the roses?

[Shotgun]

1 minute ago, D.A.F.C said:

Why not just count the roses?

Why bother? They'll be dead in a few days anyway.

[D.A.F.C]

12 minutes ago, Shotgun said:

Why bother? They'll be dead in a few days anyway.

This is why I struggled with maths because I couldn’t understand the point. When it was applied stuff like physics or electronics I found it easier.

Same with the boat riddle with the dog, chicken and corn. Just tie up the dog for a bit and go back later ffs.

[Fullerene]

38 minutes ago, sugna said:

At 10 years old, I think that iteration is probably what the question is leading in to. That and a bit of approximation, and narrowing down solutions. Just getting used to thinkng about how numbers work ,rather than speadsheeting or using algebra.

You can see that adding one-and-a-half-ish as many white as red, and well over a hundred in total, only shifts the proportion by a small amount. As an approximation, a surplus of 50% is only affecting the overall surplus by 5%, a factor of 10; so the original number is getting on for that sort of ratio w.r.t. the addition. So there are clearly many hundreds of roses there to start with.

The original batch divides by 5 (because of the 80%); and the original whites divide by 4 (same reason); and the new batch divides by 4, and the total divides by 4 (because of the 75%)*.

So... maybe try somewhere in the high hundreds, such as 800 and 1000, and take it from there.

* and the eventual total of whites divides by 3** (because of the 75%), and 4 (because new and old both divide by 4; and so on - there are often things that you can infer in order to make better approximations as you're going along, or even just to make a good initial guess.

** so the original number of whites has a remainder of 2 when dividing by 3***.*** I wouldn't expect a 10yo to reason all the way through these steps, and I'm willing to bet that I've got some of them wrong in trying to illustrate when I'm 5 minutes from sleep. But it's useful to talk some of the options through, at least.

I hope you are not a Maths teacher.

[Black Pennel]

How can you put a value on a rose ?

[Shotgun]

Courtesy of Mr. Wikipedia.

"In mathematics, a rose or rhodonea curve is a sinusoid plotted in polar coordinates."

Which I think means you get a blocked nose when you go to cold places. Either way, it changes everything.

Rose (mathematics)

[Zen Archer (Raconteur)]

9 minutes ago, Black Pennel said:

How can you put a value on a rose ?

It must be at least a grand per week to look after Fred's Mrs.

[Curmudgeon]

How can he add another 124 roses? He must have already had them in the first place, which means that they should have been included in the original number. Tell your son just to point out the duplicitous bullshit in the question.

Besides, everyone knows that X=10

Here's some more answers for the rest of this week's homework:
V=5
L=50
C=100
D=500
M=1,000

[Arabdownunder]

16 minutes ago, Curmudgeon said:

How can he add another 124 roses? He must have already had them in the first place, which means that they should have been included in the original number. Tell your son just to point out the duplicitous bullshit in the question.

Besides, everyone knows that X=10

Here's some more answers for the rest of this week's homework:
V=5
L=50
C=100
D=500
M=1,000

Ipsum bonum

[Cerberus]

The answer is 42.
It always is.
It is.

Unless the question is “how many times has Rodger seen a woman naked?”

Then the answer is zero.
Zero times.

[Mark Connolly]

2 hours ago, Arnold Layne said:

Yes, that's a good point. The problem is compounded though by the fact that he's at his mother's house tonight.

In that case, x = her fucking problem.

[tamthebam]

Roses are red, violets are blue, i failed Higher Maths twice and don't have a f*cking clue. 

I mean I can only count up to 21 and that's only when I take my clothes off..

Anyway never mind the red ones and the white ones, it's the purple roses with the hazelnut in them I like. 

[coprolite]

4 hours ago, Tony Ferrino said:

Sex?

Very kind of you. Yes please. 

[YassinMoutaouakil]

10 hours ago, Arnold Layne said:

My ten year old has this problem to solve

I have X roses. 80% are white, the rest are red. I add 76 white and 48 red. Now 75% are white. What is the value of X?

I have worked out the answer using a spreadsheet but he needs to show workings.

Any ideas?

Nicholas Lyndhurst

[Romeo]

11 hours ago, Arnold Layne said:

 

I have worked out the answer using a spreadsheet

Nonce

[throbber]

Get this thread in the fucking bin right now.

[sugna]

I had another think about this when brushing my teeth before going to bed.

Working this out by doing the algebra, for someone who has done enough maths and is reasonably numerate is simple enough; and I happen to know takes a little under the time that the electric toothbrush runs for. However:

1. Using it as a hook to get children interested in a bit of investigation by approximation etc. doesn't really appear to work, for me. The numbers involved are a bit big and clunky, and the idea that you can infer larger factors (the total has to be a multiple of 20) by deducing and combining smaller ones seems too advanced for the age range. But given(?) the ineligibility of algebra for the target age, it still seems the best guess at the teacher's intentions: "get them used to looking at big numbers".
2. I think there must be some other point to this, and I wouldn't be surprised if it's a lead-in to playing with a spreadsheet application of some sort (rather than teaching part of a maths syllabus). But there are much better sorts of problems for that.
3. So in short, it seems to me that the teacher either gave them a question at the wrong level, or had some intention about the "learning outcomes" that are not simply maths syllabus related (and seem a bit cryptic).

Let us know the aftermath (NPI), please.