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Can anyone help me work out this Geometric Progressions question?

I'm having trouble working out the answer to question 4.b), shown below. Can anyone tell me how to go about answering it?

Thanks.
2013-04-11 16.45.08.jpg363.1KB
Original post by JRChapman
I'm having trouble working out the answer to question 4.b), shown below. Can anyone tell me how to go about answering it?

Thanks.


You know the formulae right?
You have enough values?
You can use logs?

Put that together and you should be ok.
Reply 2
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JRChapman
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Original post by m4ths/maths247
You know the formulae right?
You have enough values?
You can use logs?

Put that together and you should be ok.



Actually, we haven't been taught about logs. The furthest I got in working it out was "(5/6)^n > 0.0001/54". I assume that's the point at which logs come into it...?
Reply 3
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fayled
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Original post by JRChapman
Actually, we haven't been taught about logs. The furthest I got in working it out was "(5/6)^n > 0.0001/54". I assume that's the point at which logs come into it...?


If you don't know how to use logs then all you need to know is:

If y=xn

Then n=logxy

Your calculator should have a log button with two bits to type in numbers.
(edited 11 years ago)
Reply 4
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JRChapman
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Original post by fayled
If you don't know how to use logs then all you need to know is:

If y=xn

Then n=logxy

Your calculator should have a log button with two bits to type in numbers.


Sorry, still slightly unclear about that, as when I press log on my calculator it comes up like 'log( ' ... no place for a second number?
:frown:


Edit: S'all good now, got it figured!
(edited 11 years ago)
Reply 5
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Albino
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Original post by JRChapman
Actually, we haven't been taught about logs. The furthest I got in working it out was "(5/6)^n > 0.0001/54". I assume that's the point at which logs come into it...?


How did ya get that bit?
Reply 6
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JRChapman
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Original post by Albino
How did ya get that bit?


I may well be completely incorrect, but here's how...
2013-04-11 18.48.29.jpg512.6KB
Reply 7
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Albino
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Original post by JRChapman
I may well be completely incorrect, but here's how...


Oh haha sorry just me being stupid, ya you've done it right.

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