can someone explain log please? (gcse not a-level) Watch

richageorge
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i looked it up but everything is in a-level terms, so can someone explain it in simple gcse terms? thanks

EDIT:
guys please stop arguing, its so pointless, and you all sound so stupid because you're all misinterpreting each others comments and none of you have a valid point

- i now know how to use log, so thanks if you explained it, i dont need any more explanations
- i am fully aware that logs are not required for gcse
- the only reason i asked was because there a exponential growth question, yes on a gcse 9-1 paper (i cant remember what the question was) and you had to do trial and error for it, but i didnt know how to do trial and error (stupid, i know) so my teacher told me about log
- i dont care about method marks, i'd rather have a mark for the right answer than no marks at all, and who knows, maybe i'll get method marks too

good luck if you have maths tomorrow
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3317752
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(Original post by richageorge)
i looked it up but everything is in a-level terms, so can someone explain it in simple gcse terms? thanks
Basically in ur calcultor, log helps u find out how many times to the power of something gives u something. So if u want to work out, 2^x = 32 then in ur calculator, do log2^32. This will give u the answer as 5.
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y.u.mad.bro?
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We aren't expected to know how to use log in gcse. The mark scheme will not give you the method marks if you use log.

I can help you if you have any specific question which requires log but usually, you use indices to solve the question.
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Sir Cumference
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(Original post by richageorge)
i looked it up but everything is in a-level terms, so can someone explain it in simple gcse terms? thanks
Logs is an A Level topic so to understand it requires an A Level explanation

You don't need logs for GCSE, in case you weren't aware.
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3317752
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(Original post by y.u.mad.bro?)
We aren't expected to know how to use log in gcse. The mark scheme will not give you the method marks if you use log.

I can help you if you have any specific question which requires log but usually, you use indices to solve the question.
actually exam boards have admitted that if a method is reasonable and will reproduce the correct answer in a different situation, then the marks are given.
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richageorge
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(Original post by y.u.mad.bro?)
We aren't expected to know how to use log in gcse. The mark scheme will not give you the method marks if you use log.

I can help you if you have any specific question which requires log but usually, you use indices to solve the question.
i know we're not supposed to know it but i dont know the alternative method either
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y.u.mad.bro?
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(Original post by Pretish)
actually exam boards have admitted that if a method is reasonable and will reproduce the correct answer in a different situation, then the marks are given.
True but then again, I think indices would be much easier to do.
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Sir Cumference
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(Original post by richageorge)
i know we're not supposed to know it but i dont know the alternative method either
Alternate method for what? Please give an example question.
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y.u.mad.bro?
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(Original post by richageorge)
i know we're not supposed to know it but i dont know the alternative method either
I learnt logs through this link as well as khan academy. Basic log is just a method of finding what power of a number gives you the answer. If I was saying what power of 2 gives me 32, then I would go to the log key in my calculator, put log 2^32 and this would give you an answer of 5. Therefore, 2 to the power of 5 gives you 32. Hope this helps.

Also, if you have a specific question, I can teach you how to use indices. However, I am a bit busy to find a question because I myself am revising for my maths exam tmrw
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s.xw
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(Original post by notnek)
Logs is an A Level topic so to understand it requires an A Level explanation

You don't need logs for GCSE, in case you weren't aware.
Logs are required for further/additional maths GCSEs.
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richageorge
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(Original post by y.u.mad.bro?)
I learnt logs through this link as well as khan academy. Basic log is just a method of finding what power of a number gives you the answer. If I was saying what power of 2 gives me 32, then I would go to the log key in my calculator, put log 2^32 and this would give you an answer of 5. Therefore, 2 to the power of 5 gives you 32. Hope this helps.

Also, if you have a specific question, I can teach you how to use indices. However, I am a bit busy to find a question because I myself am revising for my maths exam tmrw
thank you, and this is going to sound rather stupid but how exactly do you put it into your calculator because i did log(2^32) and i got 9.63
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richageorge
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(Original post by notnek)
Alternate method for what? Please give an example question.
well i dont have a question but say if i had 2^x = 32, how would i find x without using log?
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atsruser
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(Original post by richageorge)
i looked it up but everything is in a-level terms, so can someone explain it in simple gcse terms? thanks
"logarithm" is another word for "power". So in 10^3=1000, the logarithm is 3, and the number below it (the base) is 10.

There is a mathematical function (like sin or cos) that eats a number and spits out the power that you need to make that number from a base - this is called the logarithm-to-base-x function:

\log_{10}(1000) = 3

Here we fed 1000 into \log_{10}(). It spits out 3 - you can think of it looking down to its base number, and figuring out the power required to make the number you gave it by raising the base to that power.

There is a different log function for each base e.g. \log_2(16) spits out the number needed to make 16 by raising 2 to some power.

There's more that you can figure out about the behaviour of log functions by bearing in mind that they return powers, but I'm not sure if any GCSE syllabus requires that.
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y.u.mad.bro?
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(Original post by richageorge)
thank you, and this is going to sound rather stupid but how exactly do you put it into your calculator because i did log(2^32) and i got 9.63
not all all. You use the function of log but bear in mind there are 2 log keys. 1 of them look something like logx(x) so what you do is you put log2(32) and this gives you a result of 5.

The other log key is just log but I would recommend you not trying to understand that at this point in time because it will cause confusion if you try and understand 2 methods at the same time.
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richageorge
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(Original post by atsruser)
"logarithm" is another word for "power". So in 10^3=1000, the logarithm is 3, and the number below it (the base) is 10.

There is a mathematical function (like sin or cos) that eats a number and spits out the power that you need to make that number from a base - this is called the logarithm-to-base-x function:

\log_{10}(1000) = 3

Here we fed 1000 into \log_{10}(). It spits out 3 - you can think of it looking down to its base number, and figuring out the power required to make the number you gave it by raising the base to that power.

There is a different log function for each base e.g. \log_2(16) spits out the number needed to make 16 by raising 2 to some power.

There's more that you can figure out about the behaviour of log functions by bearing in mind that they return powers, but I'm not sure if any GCSE syllabus requires that.
that's so helpful, thank you! this is all i needed
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y.u.mad.bro?
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(Original post by richageorge)
well i dont have a question but say if i had 2^x = 32, how would i find x without using log?
These question are simple and examiners expect students to understand some powers. You will just have to remember that some numbers are powers or 2 and 3 e.g. 16, 32 and 64. however, say you had a question such as 9^x = 27^4. Your first step would be to write the two numbers as powers of 3 because you are expected to know that these two numbers are powers of 3. Rewriting the equation would give you,

(3^2)^x = (3^3)^4. Now, give that you know that when you do 1 power to the other power, you times them so this would simplify to give you 3^2x = 3^12.

Now, you take the two powers and solve them by forming an equation. 2x=12 => x=6. Therefore, 9^6 would be the same as 27^4.
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richageorge
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(Original post by y.u.mad.bro?)
not all all. You use the function of log but bear in mind there are 2 log keys. 1 of them look something like logx(x) so what you do is you put log2(32) and this gives you a result of 5.

The other log key is just log but I would recommend you not trying to understand that at this point in time because it will cause confusion if you try and understand 2 methods at the same time.
ahh i didnt realise there were 2 buttons, i was using the wrong one lol. that makes sooo much sense, thank you so much, and good luck for maths tomorrow
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Mr Dee Mented
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Yes it is an A level topic but there was a question in Paper 2 9-1 Edexcel where log could of been used that is why this person is asking incase it comes up tomorrow

(Original post by notnek)
Alternate method for what? Please give an example question.
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_gcx
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(Original post by Mr Dee Mented)
Yes it is an A level topic but there was a question in Paper 2 9-1 Edexcel where log could of been used that is why this person is asking incase it comes up tomorrow
The question was simple enough to do with basic exponent laws.
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stoyfan
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(Original post by richageorge)
well i dont have a question but say if i had 2^x = 32, how would i find x without using log?
You can break 32 down into prime factors.

Log is not in the GCSE specification so dont use it
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