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?

Thanks I asked my son. . 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

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.

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

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.

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'

0/10 for your response... 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!)

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

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