Logs are hell!

Tommy B · 5 Apr 2007 at 16:40

Been zooming through C1/C2 A level maths revision papers this afternoon. I'm doing A level but retaking the AS modules.

I simply cannot solve this easy (2 mark) question. It's driving me insane :mad:

I will actually pay someone 50p via paypal if they tell me how the hell you do this

Cheers

Biohazard · 5 Apr 2007 at 16:43

Log10 Z =

Al Vallario · 5 Apr 2007 at 16:43

Was anyone else expecting something different when they clicked on the title, gasping in horror as an image started to load?

iCraig · 5 Apr 2007 at 16:43

Al Vallario said:
Anyone else expecting something different when they clicked on the title, then gasp in horror as an image started to load?

*raises hand*

Biohazard · 5 Apr 2007 at 16:44

*raises hand*

Dr_Evil · 5 Apr 2007 at 16:44

Z = Zo * 10 -kt

log10 (Z) = log10 (zo) * log10 (10 - kt)

Tommy B · 5 Apr 2007 at 16:44

Damn! This place needs less comedians and more mathematicians

Biohazard · 5 Apr 2007 at 16:44

Dr_Evil said:
Z = Zo * 10 -kt

log10 (Z) = log10 (zo) * log10 (10 - kt)

+50p?

WotDa · 5 Apr 2007 at 16:45

Al Vallario said:
Was anyone else expecting something different when they clicked on the title, gasping in horror as an image started to load?

*raises hand* :/

Biohazard · 5 Apr 2007 at 16:45

Tommy B said:
Damn! This place needs less comedians and more mathematicians

I'm only using this as cover as I am rubbish at Mathematics!

Dr_Evil · 5 Apr 2007 at 16:46

Biohazard said:
+50p?

paypal: dr[dot]eeeevil[at]gmail[dot]com

(since no-one has proven me wrong yet)

michael baxter · 5 Apr 2007 at 16:46

I was too, I thought there was a discussion going on about burning wood. Possibly I may of been expecting a discussion on the relative merits of ash against oak, and how to dry them before combustion.

Really I did, but I'm a country bumpkin.

Biohazard · 5 Apr 2007 at 16:47

Dr_Evil said:
paypal: dr[dot]eeeevil[at]gmail[dot]com

(since no-one has proven me wrong yet)

I'll take your smug arogance as a yes, it is correct then....

Tommy B · 5 Apr 2007 at 16:47

Dr_Evil said:
Z = Zo * 10 -kt

log10 (Z) = log10 (zo) * log10 (10 - kt)

Are you sure about that?

Wouldn't it + not *? And how does log10(10-kt) get to -kt + log(10)z0?

Dr_Evil · 5 Apr 2007 at 16:48

Biohazard said:
I'll take your smug arogance as a yes, it is correct then....

No it needs 1 or 2 more steps, but it's been too long ago..... perhaps 25 p will do?

Azagoth · 5 Apr 2007 at 16:48

It's true, you can find anything on t'internet!

Bionic log! :confused:

Biohazard · 5 Apr 2007 at 16:49

lmfao!

Dr_Evil · 5 Apr 2007 at 16:49

Tommy B said:
Are you sure about that?

Wouldn't it + not *? And how does log10(10-kt) get to -kt + log(10)z0?

well that's what needs working out, but i've given u a start. and it's *, not +, if there is nothing. (AB = A*B not A+B)

Psiko · 5 Apr 2007 at 16:50

Do you know the laws of logs (which apply no matter which base you use) ?

The most important one is log(xy) = logx +logy.
We can then use this iteratively (ie. over and over again) to find that log(x^n) = nlogx.

So log(x y^n) = logx + log(y^n) = logx + nlogy.

I hope that helps.

Tommy B · 5 Apr 2007 at 16:51

Dr_Evil said:
No it needs 1 or 2 more steps, but it's been too long ago..... perhaps 25 p will do?

I would have considered it but what you wrote wasn't correct