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3.1  Logarithms Application

Example.  Multiply   using logarithms.

First we find the common logarithm of each number:         

By definition of logarithm this means:                              

So, multiplying   is the same as multiplying       

We can thus add the exponents, i.e. add the logarithms:    

which is the logarithm (exponent) of our answer.

Now we need to find the number whose logarithm is  6.4979. 

In other words, we need to find .                                                   

This is a decent approximation to .  

Note:  If you store intermediate values in your calculator, you will obtain a more accurate answer.  Ask your instructor how.

Find the following products using logarithms.  Show all work. 

1.   100 * 1000 

2.  352 * 4000

3.  23* 9821

4.  40521 * 621

5.  4290*93000000

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