# Anybody good at maths? equations?

Discussion in 'Just Talk' started by dvddvd, Jan 8, 2023.

1. ### dvddvdWell-Known Member

Im trying to get my head around this:
I want to work out how to come up with a number that I can use to make larger measurements a smaller scale version?

So if a person is 1800mm tall and i want to make a smaller version which is 85mm tall?
Then with the scale number I can use it on different objects and make them the same scale?
For example something that's 1000mm tall I can scale it so it's the same scale as the original query?

Does that make sense?

How do I work it out?

2. ### CGNScrewfix Select

you could simply divide by a nice round number such as 10, or 20, giving you 1:10, 1:20 etc.

3. ### dvddvdWell-Known Member

.
So 85mm ÷ 1800mm = 0.0472

So 0.0472 is then x by any other number to keep the same scale as the original

So for example 1000mm x 0.0472= 47.2mm which sounds right

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4. ### WillyEckerslikeScrewfix Select

To replicate those proportions you would need to multiply your original number by 0.04722.

For example 1800 x 0.04722 = 84.996

Edit: It took me longer to type the answer than work it out and you had solved it in the meantime.

5. ### quasar9Screwfix Select

Another way - ratios. In your example 85: 1800 roughly equal 1:21 rounded down. So you divide the anything full scale by 21 to get the size of the smaller model

so 1000mm on this scale is 47.6 or 47 rounded up

6. ### dvddvdWell-Known Member

thanks all, should of paid more attention in maths at school...

7. ### CGNScrewfix Select

everyday is a school day. The replies given give you a pretty much exact way of scaling dimensions. Most drawing scales though will work on rounded numbers.

8. ### I-ManScrewfix Select

Rishi has plans to sort that out

Kingscurate likes this.
9. ### FlyByNightScrewfix Select

0/10 for your maths ! 47.6 will round to 48

And at on time in modelling there was a 1:48 scale or 1/4":1'

Kingscurate likes this.
10. ### I-ManScrewfix Select

Either Divide by (rounded) 21 - eg 1800 / 21 = 85.7 - this gives you the ratio of 1:21
or Multiply by (rounded) 0.047 - eg 1800 x 0.047 = 84.6 - (this does not give you the ratio of 1:48!)

11. ### stevie22Screwfix Select

This is an ideal situation to break out the slide rule: quicker than a calculator for this sort of job.

12. ### FlyByNightScrewfix Select

Maths was right, interpretation was wrong!

I-Man likes this.
13. ### I-ManScrewfix Select

not if you know what you're calculating

14. ### stevie22Screwfix Select

It surely is if you know what you're talking about.

15. ### TiltScrewfix Select

yes, it's just 4.7222% recurring .......

16. ### quasar9Screwfix Select

The real question, how many studied maths to age of 18! up to early 70’s could leave school without any qualifications at the age of 14 and many did