Question about Casio FX991MS Scientific Calculator

# Can we find the answer to log2.5 to the base 2 using 991ms?

And can we find log with different base other than 10 like 2 or 5 or something else??

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Use one of the relations
log_b(a)=log_10(a)/log_10(b) or
log_b(a)=ln(a)/ln(b)
log_2(2.5)=(log_10(2.5))/log_10(2)=1.32198095

Posted on Apr 23, 2014

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Posted on Jan 02, 2017

In any scientific calculator log2(n) can be  calculated with either ln or log function as follows

Log2(n)= ln(n) / ln(2)

Or
Log2(n)=log(n) / log(2)

both will give nearly the same answers

Posted on Apr 24, 2009

Your calculator knows only the decimal logarithms log or log_10 and the natural logarithms (ln or log in base e).
So you cannot compute directly the logarithms in any bases other than 10 and e.
A workaround consists in using the relation
log_b(a)= (log_10(a) ) / (log_10 (b))
or the relation
log_b(a)= ln(a)/ln(b)

Similarly
log_2(0.3)=ln(0.3)/ln(2)
As to the multiplicative factor you had at the beginning of your expression, just multiply the value obtained by one on the formulas above (both formulas will give the same result) by 0.3

Posted on Jul 24, 2010

SOURCE: How do I do logs

Most calculators can't do logs in different bases, but you can solve for the answer this way:

Let's say you need to take the log of 5 in base 3. This can also be written as log5 (base 10)/log3 (base 10).

A more technical solution can be found here: http://oakroadsystems.com/math/loglaws.htm#NewBase

Posted on May 25, 2011

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## Related Questions:

### How do I find log with a different base (not 10)?

Calculate the log (base 10) of the number, then divide the result by the log (base 10) of the base.
For example, to calculate the base-3 log of 9, calculate the log of 9 to get 0.954 . Divide that by the log of 3 (about 0.477) to get 2.0 .
Since 9 is 3 squared, the log base 3 of 9 is 2, as we just calculated.

Mar 28, 2012 | Office Equipment & Supplies

### How to find inverse of log in a casio 991ms calci?

The inverse of the natural logarithm (in base e) is the EXPONENTIAL function (e^x). It shares the same physical key as the LN function. One is accessed directly and the other through the SHIFT key. The inverse of the logarithm in base 10 is the function 10^x. Both functions share the same physical key as described above.
More generally if y=log(in base b) of x =log_b(x) then x=b^(y). The base must of course be a non-zero positive number.

Aug 25, 2011 | Casio FX-115ES Scientific Calculator

### How do I do logs with different bases (bases other than 10)

Most calculators can't do logs in different bases, but you can solve for the answer this way:

Let's say you need to take the log of 5 in base 3. This can also be written as log5 (base 10)/log3 (base 10).

A more technical solution can be found here: http://oakroadsystems.com/math/loglaws.htm#NewBase

May 25, 2011 | Casio FX-9750GPlus Calculator

### How do you convert 4726 to base 10?

4726 seems to already be on base 10
it's 4*10^3 + 7*10^2 + 2*10^1 + 6*10^0

Mar 17, 2011 | Casio FX-115ES Scientific Calculator

### How to calculate 0.3log(base 2)0.3 using fx-991ms calc

Your calculator knows only the decimal logarithms log or log_10 and the natural logarithms (ln or log in base e).
So you cannot compute directly the logarithms in any bases other than 10 and e.
A workaround consists in using the relation
log_b(a)= (log_10(a) ) / (log_10 (b))
or the relation
log_b(a)= ln(a)/ln(b)

Similarly
log_2(0.3)=ln(0.3)/ln(2)
As to the multiplicative factor you had at the beginning of your expression, just multiply the value obtained by one on the formulas above (both formulas will give the same result) by 0.3

Jul 18, 2010 | Casio FX-115ES Scientific Calculator

### How to calculate ln using fx-991ms

Hello, There is a key for that, the one labeled [ln] for natural logarithm. For log in base 10 use the key [LOG] [LN] 10 [ENTER] gives 2.302585093. As you certainly know, you cannot take the logarithm of a negative number, nor of Zero.
Hope it helps.

Nov 01, 2009 | Casio FX-300MS Calculator

### How can I use the Log function on my calculator?

Hi ;

for log base 10 use the the "log" key

example :

log(2) + log(3) = log(6)

enter 2 press the log key you will get 0.30102999 press the '+" key than 3 log you should get 0.47712125 for it Press the "=" or enter and you should get 0.778151250 for a answer than press inv or 2nd log and you should get 6 for a answer

and that all there is to it

Oct 07, 2009 | Texas Instruments BA-II Plus Calculator

### How to calculate logrithm of base of any number in fx-991ms

you need the change of base formula:

log base b of m is ln m / ln b

So- to find log base 2 of 8, simply find ln8/ln2

(from Wikipedia - the proof also follows if you want to go look it up)
While there are several useful identities, the most important for calculator use lets one find logarithms with bases other than those built into the calculator (usually loge and log10). To find a logarithm with base b, using any other base k:

Oct 06, 2009 | Casio FX-300MS Calculator

### How do i perform the calculation of log (base 2) 8? The answer should be 3....that is it is the inverse calculation of 2 cubed =8. Can any one help with the log calculation?

Yes look you can't enter the base in calculators it's default 10 so use:
log x base y = log x / log y
log (x*y) = log x + log y
log (x/y) = log x - log y
so instead of log 8 base 2 input log 8 / log 2 it's easy
hope you understand :)

Feb 21, 2009 | Sharp EL-531VB Calculator

### How to calculate log value in calculator with different base value

In any scientific calculator log2(n) can be  calculated with either ln or log function as follows

Log2(n)= ln(n) / ln(2)

Or
Log2(n)=log(n) / log(2)

both will give nearly the same answers

Dec 08, 2007 | Casio FX-300MS Calculator

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