Discussion about math, puzzles, games and fun. Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ π -¹ ² ³ °

You are not logged in.

- Topics: Active | Unanswered

**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 15,658

I just wantto know how in the world do you plan on getting 4900 and 5100?

Here lies the reader who will never open this book. He is forever dead.

Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment

Offline

**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,532

hi Stefy,

Previous post: Yes, you are of course correct. It was that word 'easily' that put me off.

So that makes it:

Bob

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

Offline

**anna_gg****Member**- Registered: 2012-01-10
- Posts: 113

bobbym wrote:

Hi anna_gg;

You eliminated all the possible weights that are not multiples of 100. Is that okay?

Yes, because the problem says the grocer only sells in multiples of 100 grams.

Offline

**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,532

hi anna_gg

That was quite a problem you set.

As you can see we are still working on it.

I haven't had a chance to revise post 5 yet because Stefy keeps finding new values.

Just going to adjust my previous so it fits the page better.

Bob

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

Offline

**anna_gg****Member**- Registered: 2012-01-10
- Posts: 113

bob bundy wrote:

LATER EDIT: I am in the process of correcting this 'solution'. I am optimistic that I'll get there some time (... length of time unspecified ...)

I am assuming the grocer has a limitless supply of weightless bags to put his derived flour weights into.

How about subscripts?

A weight that exists at the start will have zero as its subscript.

A weight derived at 1st weighing will have subscript 1.

I did have some others here, not multiples of 100. I have now removed these.

I do not think something like 4850 can later generate a multiple of 100 except by restoring the number that made it.

This conjecture needs proving (or a counter example).

I believe this is a complete list of 1st weighings.These 1st weighing amounts are put into bags and become additional 'weights'.

Now, what can be made at the 2nd weighing?

Theorem: (i) Where different flour bags are used the subscript total to achieve a new weight must be strictly less than the subscript of the new weight. *

(ii) but if the same bag is used in several stages the subscript total to achieve a new weight

need not count this bag repeatedly

to make this total strictly less than the subscript of the new weight. An example of this is shown later in achieving 1400_3 and 1600_3.This theorem needs to be modified. My thanks to anonynmstefy for pointing this out.

* so here, 2 > 1 + 0 + 0

Now those 'weights' can also be bagged up to use at the next stage.

3rd weighings

I cannot find a way to do 1400.

But anoninmstefy did:

I think that's it. If you spot any more, please let me know.

Oh darn it! I've just noticed that 5000. That'll be 5000 against 5000.

So the list needs some additions. ..... Tomorrow perhaps. No better still, you've seen the method, I'll leave it as an exercise for the reader.

Additionally, for whatever amount,

x, that can be measured out, the amount10000 - xis also available for sale which doubles the list!List so far:

I'm assuming the probability is easy to get from here.

Bob

Why not also

10000_1

5000_1

100_1

9900_1

200_1

9800_1

4900_1

5100_1

300_1

9700_1

500_1

9500_1

*Last edited by anna_gg (2012-04-14 21:59:45)*

Offline

**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,532

Yes to all under 4000 but not 9500, 9700, 9800, 9900, 10000. I don't think you can use that flour twice.

4900_1

5100_1

Not both for total flour reasons. And they would only be worth making if you could use them together and that just makes amounts you have already got.

Bob

ps. Did you know the list was going to be this long when you posted this?

pps. Still to find or prove impossible:

and their complements.

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

Offline

**anna_gg****Member**- Registered: 2012-01-10
- Posts: 113

These are "possible" alternative weighings, so why not use them?

To make 9500, for example, you take the total quantity of 10000 (no need to weigh it, as we already know it's 10000) and remove the quantity required to balance the 200 and 300 g weights together; so the remaining is 9500.

Same way with 9700 (we use only the 300g weight), 9800 (only the 200g weight), 9900 (we use both, one in each pan, to weight 100g, so the remaining is 9900).

Offline

**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,532

hi anna_gg

Yes got that back in post #5

Additionally, for whatever amount, x, that can be measured out, the amount 10000 - x is also available for sale which doubles the list!

Post #27 gives the best list so far with contributions from several sources.

And post #31 shows those that haven't been found yet.

Bob

Offline

**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 15,658

Hi bob

See #20 for 2000 and as for 3600 you can take the first two measurements from #21 which makes 1800g and just double it in the last measurement to get 3600.

Here lies the reader who will never open this book. He is forever dead.

Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment

Offline

**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 15,658

And as for the 4900 and 5100 how do you know when you have put the 4900 on one side?

Here lies the reader who will never open this book. He is forever dead.

Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment

Offline

**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,532

Same as all of them really.

You just pour a bit and see how the balance moves.

If you have put too much in one pan you move a bit across.

This is a maths puzzle; not a lesson on running a grocer's shop!

Bob

Offline

**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 15,658

Ok,but did you see #34?

Here lies the reader who will never open this book. He is forever dead.

Offline

**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,532

Yes, sorry haven't had time to re-write the list as I've been helping zetafunc.

Suggestion: Copy my list yourself into a new post, adding your values to it. ** I am confident you are right! **

What? You want me to play the teacher game and mark all of your work before putting it up on the wall?!

Huh! not likely, I've retired!

Bob

Offline

**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 15,658

I didn't get most of your post ,but it doesn't matter...

Here lies the reader who will never open this book. He is forever dead.

Offline

**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 15,658

Hi bob

I've got an idea for 4700. Stay online while I post it.

Here lies the reader who will never open this book. He is forever dead.

Offline

**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 15,658

Here 600_2,3 means that 600 grams was aquired between 2nd and 3rd measuring.

*Last edited by anonimnystefy (2012-04-15 08:10:53)*

Here lies the reader who will never open this book. He is forever dead.

Offline

**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,532

Oh that's very clever. the list of 'not yet done' values is getting smaller and smaller. I wonder if it will shrink all the way down to the empty set.

I had hoped to pass on the job of up-dating the list but it looks like I'll have to do it ... but later as I'm still catching up on other posts.

Meanwhile, keep looking. Only a few to go.

Bob

Offline

**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,532

I know: I'll just write the list of 'not yet done'. It'll be easier.

Bob

Offline

**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 15,658

4800:

And as we know: 4800=2500+2300.

Here lies the reader who will never open this book. He is forever dead.

Offline

**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,532

Excellent! I'll just sit here and tell you you are brilliant every few minutes.

Bob

Offline

**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 15,658

4600:

Here lies the reader who will never open this book. He is forever dead.

Offline

**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 15,658

4500:

Now we add 2000 and 2500 to get 4500.

Here lies the reader who will never open this book. He is forever dead.

Offline

**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,532

You could do this bit yourself you know!

arhhrr! But then, who is going to tell you how impressive that is!

Bob

Offline

**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 15,658

It is not impressive at all. And the list is helping me. The typing of that would create additional struggles because I am on my phone.

Here lies the reader who will never open this book. He is forever dead.

Offline

**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 15,658

4400:

Here lies the reader who will never open this book. He is forever dead.

Offline