# Thread: Mystery Money Grid Puzzle - How do you solve?

1. ## Mystery Money Grid Puzzle - How do you solve?

New to these forums, so hi to all!

I'm trying to help my 9 year old daughter with her homework. She has been given a 'Mystery Money Grid' puzzle (as pictured below). She has sat looking at it for about 45 minutes but has no idea where to start.

Now, I've been sitting looking at it for ages and other than randomely writing in numbers to see if it all works I have no idea of the 'proper' way to solve this puzzle. I don't want to just work out this particular puzzle (which I guess I could do in time) because I want to be able to tell her 'how' to work it out.

Is there a technique to solving this type of puzzle?

Thanks,

Mike.

IMG_4638.jpg (Apologies for size and being on it's side, the original file is the right way up?!?!?)

2. Originally Posted by Banzaibrothers
I'm trying to help my 9 year old daughter with her homework. She has been given a 'Mystery Money Grid' puzzle (as pictured below). She has sat looking at it for about 45 minutes but has no idea where to start.

Now, I've been sitting looking at it for ages and other than randomely writing in numbers to see if it all works I have no idea of the 'proper' way to solve this puzzle. I don't want to just work out this particular puzzle (which I guess I could do in time) because I want to be able to tell her 'how' to work it out.

Is there a technique to solving this type of puzzle?
There is no 'proper' way to do it, and nothing one would be explicitly taught; it is a logic puzzle, in which you just have to try different possibilities, saving time as much as possible by reducing the number of things to be tried. The skill of figuring out how to solve a puzzle you've never seen before (patience, orderliness, ...) is probably more important than any particular method you might be taught!

As I understand it, the sum of each row and column must be the amount indicated, and there must be a coin in every cell. In order to solve it, you need to know what coins are used in your country.

Since I don't know your coins on sight, I had to look carefully; to make it easier to work with, I have made a table that just shows values:

 3.21 4.41 3.27 0.57 1.74 2.93 1.34 1.00 0.20 0.87 0.05 0.20 4.52 2.00 0.02 3.32 0.20 1.00 3.21 1.00 1.00 2.87 0.05 0.20

Here is how I've approached it, which may not be the only way, but makes a lot of sense to me. I first found, for each row and column, how much more money is needed, and how to make that amount with the right number of coins. If my guess is correct that you have coins of 2.00, 1.00, 0.50, 0.20, 0.10, 0.05, 0.02, and 0.01, then I think they designed this so that in each case there is only one way to get the right amount, so we know exactly what coins are needed. For example, in the first row we need four coins adding to 0.14, which must be 0.05+0.05+0.02+0.02. Oops -- it could be 0.10+0.02+0.01+0.01, so I was wrong. There may be more possibilities to consider than I hoped.

Having written these values at the right of each row and the bottom of each column, I can look for a way to determine where each goes. I leave it at that; I haven't completed the puzzle, but it looks like it will not be too hard from this point.

But keep in mind that this is meant to be a challenge! And also, since there is no way to teach a specific technique, it has to be thought of as fun. And it has to be no shame if your daughter doesn't figure it out. It's just a game.

3. It's not perfectly clear to me what units are available. For example: Can you use a shilling (12 pence)?

What units CAN be used would be an important piece of information.

4. Yes, good point. I should have said we have 1p, 2p, 5p, 10p, 20p, 50p, £1 and £2 (1, 2, 5, 10, 20, 50, 100 and 200).

The way you are suggesting is how I have now done it. But it's taken me over an hour (there is definitely more than one way to solve each row/column).

I'm glad I'm not missing a simple trick to solving it and it is just a case of working through it.

But there is no way my 9 year old daughter would be able to get through it in a logical manner to get a solution.

5. Originally Posted by Banzaibrothers
… Apologies for size and being on it's side, the original file is the right way up?
You were holding your phone sideways, when you took the picture. (This forum does not rotate images.)

6. Thanks. I know I couldn't find an easy way of solving the puzzle (although it would appear the solution I did find is the only solution) but I can use a phone and a computer. Image was taken the right way up (portrait). When I view the file on my computer it's the right way up. When I go 'insert image, browse and click on the image the thumbnail is the right way up. Then I click open, and upload and the image appears on its side. Weird.

mathforum.jpg

This image was a screen shot of what I see when I select the file. You can see the image is the correct way up. Interestingly this image has loaded in without rotation. As I say, weird.

7. You're using software that automatically rotates the display for you; this forum doesn't do that. Use the Preview Post button, to check how your post will render. If an image is not properly oriented, then you will need to manually edit the image file and rotate it. Do you know how?

8. Automatically rotates the display? Are you saying all iPhone photos, even if taken in Portrait are actually landscaped images? But that my phone, Finder on the Mac and every other peice of software I view it through know what my intentions were when I took the photo so rotate it to be the right way up, then when I import it to this forum it gets rotated back to landscape because it's actually a landscape image? I've never come across that before. I'm not saying it's not what happens, just that I never knew that was what was happening.

Yes, I do know how to rotate an image in editor but it would be the first time I would have to rotate an image to look wrong so that when I import it, it looks right; if that makes any sense? I also used the preview post function but again, didn't imediately think of rotating it to look wrong to make it right.

Anyway, I think we might be loosing track of the purpose of the thread

9. Originally Posted by Banzaibrothers
I'm glad I'm not missing a simple trick to solving it and it is just a case of working through it.

But there is no way my 9 year old daughter would be able to get through it in a logical manner to get a solution.
Why not? Yes, these sorts of exercises are tedious, but there's nothing terribly complicated or advanced about them. One need only apply patience in an orderly fashion.

Please don't doubt your daughter! Have faith in her! Let her know that, yes, even "just a girl" can indeed do this!

10. This may be helpful, as an example:

https://www.algebra.com/algebra/home...on.152564.html

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