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Referring to log base 10

2007-12-21 08:30:18 · 6 answers · asked by Vi A 1 in Science & Mathematics Mathematics

6 answers

log(12.5) is positive
log(0.8) is negative

If we add them we would expect an integer result if they had the same decimal.

Remember this rule of logs:
log(a) + log(b) = log(ab)

log(12.5) + log(0.8)
log(12.5 * 0.8)
log(10)
= 1
This is an integer result.

Because:
log(12.5) + log(0.8) = 1

The answer is yes, they have the same repeating decimal sequence.

2007-12-21 08:34:04 · answer #1 · answered by Puzzling 7 · 0 1

using the log rules and the fact that:
10/0.8 = 12.5

we get:

log 12.5 = log 10/0.8 = log 10 - 0.8 = 1 - log 0.8

2007-12-21 08:38:45 · answer #2 · answered by iheart808 3 · 0 0

I'm assuming that you are taking logs in base 10. Use the fact that log(a/b) = log(a) - log(b)

log(12.5) = log(100/8) = log(100) - log(8) = 2 - log(8)
log(0.8) = log(8/10) = log(8) - log(10) = log(8) - 1

Note that both terms are a combination of an integer and
log(8)

2007-12-21 08:36:15 · answer #3 · answered by Astral Walker 7 · 1 0

They have the same decimal sequence because their mantissas are identical in base 10.
Log(12.5) = Log(10) + log(1.25) = 1 + log(1.25)
0.8 is the reciprocal of 1.25, so
Log(0.8) = - log(1.25)
Adding the 1 to log(1.25) does not change its decimal part.

2007-12-21 09:18:52 · answer #4 · answered by Helmut 7 · 0 0

log 12.5 = log (100/8) = 2 - log8
log 0.8 = log(8/10) = log8 - 1

I don't know is there any relate to ur question

2007-12-21 08:37:34 · answer #5 · answered by tinhnghichtlmt 3 · 0 0

Puzzling was right, except that the numbers a non-repeating irrationals. They go on forever without repetition.

2007-12-21 09:06:59 · answer #6 · answered by Tom V 6 · 0 0

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