Converting Between Units (Cambridge (CIE) IGCSE Biology)
Revision Note
Converting Between Units: Extended
Extended Tier Only
Using millimetres and micrometres as units
The table below shows how millimetres are related to two other measures of length
What this basically means is that 1mm = 1000µm and 1cm = 10,000µm
This usually comes up in questions where you have two different units and you need to ensure that you convert them both into the same unit before proceeding with the calculation
For example:
Example extended magnification question
Remember 1mm = 1000µm
2000 / 1000 = 2 so the actual thickness of the leaf is 2mm and the drawing thickness is 50mm
Magnification = image size / actual size = 50 / 2 = 25
So the magnification is x 25 (NO UNITS)
Examiner Tip
If you are given a question with two different units in it, make sure you convert them to the same unit before doing your calculation.If you don’t, there is a good chance that your answer will be the same as one of the incorrect options in a multiple choice question so you may think you got it right when, in fact, you haven’t!The following diagram may help with unit conversion between mm and µm:
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