The Student Room Group
Reply 1
factorise 150 into prime factors? I'm not sure it'll work, but it is worth a try...

edit: won't work work me... hence a bad idea probably:tongue:
Reply 2
lilydelarocks
1) Given that a = log(10)2 and b = log(10)3, find the expressions in terms of a and b for [(10) meaning a small 10]

a) log(10)1.5


Here
Reply 3
OH yes I forgot bout that..I've just taught myself this topic as I was never taught this by a teacher so Im more likely to make mistakes with this topic...

Unfortunately for me, I've been set homework to do a whole sheet on Exponentials and Logarithms..
Reply 4
Question: does that mean b) is 3a + b..?

Explanation:
log(10)24
= log(10)2³ x log(10)3
= 3log(10)2 x log(10)3
= 3a + b

EDIT: ok I see I am correct..YIPEEEE
Reply 5
lilydelarocks
OH yes I forgot bout that..I've just taught myself this topic as I was never taught this by a teacher so Im more likely to make mistakes with this topic...

Unfortunately for me, I've been set homework to do a whole sheet on Exponentials and Logarithms..


I think you should have been given log(10) 5
Reply 6
steve2005
I think you should have been given log(10) 5

I agree, I was scratching my head for trying to figure that one out with multiples of 2 and 3, which I coudn't...
Reply 7
OK thanks guys..

But Im stuck on another question:
4log(3)x - 5 = 0

I have:
4log(3)x - log(10)10^5 = 0

But not sure what to do next...Im stuck with bringing the
log(10)10^5 over to the other side and doing something else but then again, Im not sure what I would do next if i do that..
Reply 8
lilydelarocks
OK thanks guys..

But Im stuck on another question:
4log(3)x - 5 = 0
..


If you want x then the answer is 3.948(3 d.p)
Reply 9
OK Thanks

Sorry to bother you guys again on this topic..
but i have another question:

log(3)x³ - 5log(3)x = 4

Is this right?
log(3)x³/5log(3)x = 4
1/5x² = 4
x² = 20
x = 4.472135955
lilydelarocks
OK Thanks

Sorry to bother you guys again on this topic..
but i have another question:

log(3)x³ - 5log(3)x = 4

Is this right?
log(3)x³/5log(3)x = 4
1/5x² = 4
x² = 20
x = 4.472135955

No. The answer 1/9

Many calculators can work out logs in different bases. e.g casio fx 83ES So you can check your answers.
Reply 11
steve2005
I think you should have been given log(10) 5


log(10) 5 = 1 - log(10) 2 :wink:

lilydelarocks: You should be able to use this to work out the c) part of your first question.
ukgea
log(10) 5 = 1 - log(10) 2 :wink:


Clever. Using your hint I have done it slightly different.
Reply 13
Oh ok thanks..man I'm going to really struggle with this worksheet and this whole topic in general :frown:...
lilydelarocks
Oh ok thanks..man I'm going to really struggle with this worksheet and this whole topic in general :frown:...

Do you know about MathsNet ?

http://www.mathsnet.net/asa2/2004/c25loglaws_1.html
Reply 15
I don't even have an idea of how to work out this question:

An initial investment of £1000 is places into a savings account that offers 2.2% interest every 3 months. The amount of money in the account £P, at the end of t years is fiven by

P = 1000 X 1.022 ^(4t) ....( and that's a mutiply sign btw)

Find, to the nearest year, how long it will take for the investment to double in value. (4 marks)
i.e. you have to solve 2000=1000×1.0224t2000=1000\times1.022^{4t}

edit: t must be rounded up to nearest integer if I'm not missing anything
lilydelarocks
I don't even have an idea of how to work out this question:

An initial investment of £1000 is places into a savings account that offers 2.2% interest every 3 months. The amount of money in the account £P, at the end of t years is fiven by

P = 1000 X 1.022 ^(4t) ....( and that's a mutiply sign btw)

Find, to the nearest year, how long it will take for the investment to double in value. (4 marks)


This is a hint, while I figure out what is needed....
lilydelarocks
.


I guess I have been beaten.

Edit: You can use ln or log base 10 or any other logarithm base. Most calculators can work out natural logs and logs to base 10.