You should trust the calculations and not the ruler. The arithmetic will always give the correct answer, assuming you press the right buttons on your calculator - unless of course you're trying to work out 2 + 2 ÷ 2 = :smiling3: :smiling3: :smiling3:!
It more likely that the markings on your ruler have not been scribed accurately.
I don't know why you need a special calculator for scales. There's only a couple of things to remember:
ALWAYS use millimetres as your start measurement.
From real to scale size, divide by the scale.
From scale to real size, multiply by the scale.
The answers you get will be the measurement you want in millimetres.
If your answer looks silly, you've done your calculation the wrong way round.
It more likely that the markings on your ruler have not been scribed accurately.
I don't know why you need a special calculator for scales. There's only a couple of things to remember:
ALWAYS use millimetres as your start measurement.
From real to scale size, divide by the scale.
From scale to real size, multiply by the scale.
The answers you get will be the measurement you want in millimetres.
If your answer looks silly, you've done your calculation the wrong way round.
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