Well, I rarely take such a negative view, however in this case we have a question on the basic math, which only requires a bit of research on the net even if you forgot that bit (unlike the original question, which was about metrology methods and completely relevant in this section).

That suggests that I've failed to make myself clear, my bad.

My suggestion is that some people develop a blind spot, around fractions and percentages, where they fail to see that it's just basic arithmetic. My other half goes into a blind panic when presented with irrational fractions, or fractions that don't have a power of 2 on the bottom, but if presented the same calculation as a series of multiplications and divisions can do it in her head. I'm sure that there must be variants on the word dyslexia but applied to fractions and percentages.

Add to that, when starting out, some formulae for things electronic, even basics like resistors in parallel, can seem like magical incantations because of a failure on those teaching (or writing books) to provide adequate explanation of their derivation. I certainly remember when it felt like that to me for some things - I got handed R

_{e} =

^{25}/

_{Ic(in mA)} without any decent explanation, let alone any mention of the word transconductance or our old friend V

_{T} =

^{kT}/

_{q}.

Combine the two and you have a perfect recipe for confusion. To you, to me, it's obvious that it's just basic maths, but some people may need a hand to see that before they realise that they are already equipped to tackle the problem. Not seeing the forest for the trees and all that.

Of course I may be being too charitable and perhaps the OP really is a lazy sod but I'm prepared to give him the benefit of the doubt.

I

**do** agree that this is one the OP ought to be able to work out for himself, he perhaps just needed that pointed out first.

So,

**001**, Alex and I both think you can probably work that out for yourself, even if you have to think for a few minutes first. If you get stuck, you can always ask for help.