Help with a mathematics formula please anyone?

[TonyRPH]

My maths is not very strong - and I'm trying to perform a complex (to me!) calculation, but I cannot seem to master it.

I am using this equation as an example: (ignore the leading ":" it's just a bit of text I captured by mistake)



So as I read that, it's SQRT(3.374e-6)squared / (1.228)squared * 100 = 0.000275%

But no matter how many variations I enter into my calculator(s!), I cannot arrive at the given answer.

I have tried breaking the calculations down into individual chunks - and also enclosing everything inside parenthesis i.e. SQRT((xyze-6)SQ/(abc)SQ)*100

Can anybody help please?

I'm hoping the sample equation I have is correct!

Thanks in advance.

[Fugazi]

100* sqrt((3.374*mu*Vrms)^2/(1.228*Vrms)^2)

Should work? What are the values of Vrms and Mu?

[TonyRPH]

Fugazi said:

100* sqrt((3.374*mu*Vrms)^2/(1.228*Vrms)^2)

Should work? What are the values of Vrms and Mu?

What is "mu"?

The value of Vrms is 3.374uV

3.374uV is 3.374e-6v or 0.000003374v - correct?

Can you explain what the "mu" is please?

[Fugazi]

mu is the 'u like' symbol

Edit.. sorry doing this on my phone... It's not a term it's a prefix... I get it now... Too small to read on this screen with my mole eyes!

[georgetaylorPH]

This works fine, you have u = ten to the minus 6 correct already

100*SQRT((0.000003374)^2/(1.228)^2)=0.000274756

[TonyRPH]

Trying your suggested method (discarding the "mu" confusion) I get 0.68105129

Gor the avoidance of any doubt on my 'old skool' calculator...

[TonyRPH]

Aha - I think I have fallen foul of the order in which the calculator performs the calculations.

[alock]

You need a better calculator. I use HiPER Calc on Android.

[Chester draws]

edited to rotate

Edited by Chester draws on Wednesday 26th April 15:29

[TonyRPH]

Very nice - I'll try that on my tablet (phone is a Microsoft Lumia and given the lack of apps...)

My calculators were getting screwed up with the scientific notation I think.

Thanks for the help everyone.

Chester draws said:

A most appropriate username!! (draws) :P

[Northbloke]

TonyRPH said:

Trying your suggested method (discarding the "mu" confusion) I get 0.68105129

You can't discard the mu confusion...that's where you're going wrong.

The numbers in your equation are written in standard form so "3.374 mu" means 0.000003374 in longhand.

Plug that in and it works.

(ah I see others have done it already and more practically)
(edit for typo)

[Halmyre]

I get 2.747 x 10^-4 = 0.000275 near as dammit.

Breaking it down:

Step 1: 3.374 x10^-6 squared = 1.138 x 10^-11

Step 2: 1.228 squared = 1.508

Step 3: divide Step 1 by Step 2 = 7.546 x 10^-12

Step 4: square root of step 3 = 2.747 x 10^-6

Step 5: Step 4 x 100 = 2.747 x 10^-4

[Chester draws]

TonyRPH said:

A most appropriate username!! (draws) :P

It's what works for me! And how I show my kids, break It down and take it one step at a time. So mrather than one big sum, you make a number of smaller ones.

[TonyRPH]

As it happens, I was using the wrong button on my calculator to raise the number to -6

I was using Ex instead of 10x !

Solved!

[EliseNick]

You can cancel the square root and the powers of two.

[V8LM]

sqrt((3.374 mu Vrms)^2 / (1.228 Vrms)^2) * 100 = 0.000275 %

mu is micro = 1x10^-6

sqrt((3.374 mu Vrms)^2 / (1.228 Vrms)^2) * 100

3.374 1x10^-6 / 1.228 * 100 = 2.748x10^-6 = 0.00000275

Edited by V8LM on Thursday 27th April 07:28

[Monty Python]

Simple issue - the top value is in microvolts (uV) whereas the bottom is in volts. Once they're both expressed in volts it works fine.

Edited by Monty Python on Thursday 27th April 08:08

Edited by Monty Python on Thursday 27th April 08:09

Edited by Monty Python on Thursday 27th April 08:10

[TonyRPH]

EliseNick said:

You can cancel the square root and the powers of two.

So you can...

Or at least I got the same result using this method.

So why add the additional complication in the first place?

[EliseNick]

TonyRPH said:

So you can...

Or at least I got the same result using this method.

So why add the additional complication in the first place?

No idea! What's the context?

[V8LM]

TonyRPH said:

To be strict, this equation is wrong as the % symbol should be read the same as 0.01.

So either remove the * 100 or remove the %, but you shouldn't have both.