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Logarithms, a level maths

Can someone please tell me how to answer this question.2E2EF412-E7BA-4194-B7F0-DAB263CF4E60.jpg.jpeg question 9 (ii)
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Agrey
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Original post by Hannahkisley
Can someone please tell me how to answer this question.2E2EF412-E7BA-4194-B7F0-DAB263CF4E60.jpg.jpeg question 9 (ii)

10^7.4 x 63000
if earthquake strength = log (energy / 63000)

then log (energy / 63000) = 7.4

so the power of 10 that gets you energy/63000 is 7.4

so 10^7.4 = energy / 63000
so 10^7.4 * 63000 = energy
Original post by trou_noir
if earthquake strength = log (energy / 63000)

then log (energy / 63000) = 7.4

so the power of 10 that gets you energy/63000 is 7.4

so 10^7.4 = energy / 63000
so 10^7.4 * 63000 = energy


Thank you, makes sense now, I was on the complete wrong lines
Original post by Hannahkisley
Thank you, makes sense now, I was on the complete wrong lines


No worries, there is another way of working it out using the rule that

log x - log y = log (x/y)

so log energy - log 63000 = 7.4

so 7.4 + log 63000 = log energy

then just use your calculator to work out the log of 63000. you will get the power of 10 that gives the energy result. so raise 10 to that power = energy

i always get confused when i do it that way though!

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