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7.8 - Solving Using Properties of Logs
Contributed by: Luckhaupt
This assignment uses the information from the video
yesterday throughout. If you've not yet watched the
video or you just need some extra help, go back to 
yesterday's video and it should help a lot.
Let's start with a couple things we know:
log3(2) = 
log3(8) = 
Let's start with a couple things we know:
log3(2) = 
log3(8) = 
log(8)
log(3)
log(3)
log(2)
Let's start with a couple things we know:
log3(2) = 
log3(8) = 
log(8)
log(3)
log(3)
log(2)
= 0.631
= 1.893
How can we use this information to find log3(16)?
Let's start with a couple things we know:
log3(2) = 
log3(8) = 
log(8)
log(3)
log(3)
log(2)
= 0.631
= 1.893
How can we use this information to find log3(16)?
We know that log3(16) = 
Let's start with a couple things we know:
log3(2) = 
log3(8) = 
log(8)
log(3)
log(3)
log(2)
log3(8*2)
= 0.631
= 1.893
How can we use this information to find log3(16)?
We know that log3(16) = 
But the log rules tell us that:
log3(8*2) =
Let's start with a couple things we know:
log3(2) = 
log3(8) = 
log3(8)+log3(2) = 
log(8)
log(3)
log(3)
log(2)
log3(8*2)
= 0.631
= 1.893
How can we use this information to find log3(16)?
We know that log3(16) = 
But the log rules tell us that:
log3(8*2) =
Let's start with a couple things we know:
log3(2) = 
log3(8) = 
log3(8)+log3(2) = 
log(8)
log(3)
log(3)
log(2)
We know these values from above
log3(8*2)
= 0.631
= 1.893
How can we use this information to find log3(16)?
We know that log3(16) = 
But the log rules tell us that:
log3(8*2) =
Let's start with a couple things we know:
log3(2) = 
log3(8) = 
log3(8)+log3(2) = 
log(8)
log(3)
log(3)
log(2)
We know these values from above
log3(8*2)
= 0.631
= 1.893
How can we use this information to find log3(16)?
We know that log3(16) = 
But the log rules tell us that:
log3(8*2) =
Let's start with a couple things we know:
log3(2) = 
log3(8) = 
log3(8)+log3(2) = 1.893+0.631 = 2.524
log(8)
log(3)
log(3)
log(2)
We know these values from above
log3(8*2)
= 0.631
= 1.893
Remember, there are 4 Properties that we use:
Remember, there are 4 Properties that we use:
1) Multiplying logs is the same as adding the  logs of the quotientslog4(4*5) = log4(4)+log4(5)
Remember, there are 4 Properties that we use:
1) Multiplying logs is the same as adding the  logs of the quotientslog4(4*5) = log4(4)+log4(5)
2) Dividing logs is the same as subtracting the  logs of the divisorslog2(8/3) = log2(8) - log2(3)
Remember, there are 4 Properties that we use:
1) Multiplying logs is the same as adding the  logs of the quotientslog4(4*5) = log4(4)+log4(5)
2) Dividing logs is the same as subtracting the  logs of the divisorslog2(8/3) = log2(8) - log2(3)
3) Log exponents can be written in front of the loglog2(8)3 = 3*log2(8)
Remember, there are 4 Properties that we use:
1) Multiplying logs is the same as adding the  logs of the quotientslog4(4*5) = log4(4)+log4(5)
2) Dividing logs is the same as subtracting the  logs of the divisorslog2(8/3) = log2(8) - log2(3)
3) Log exponents can be written in front of the loglog2(8)3 = 3*log2(8)
4) Change of base for calculatorslog2(8) = 
log(8)
log(2)
In the following problems I'll start by giving you a couple of 
log values. You'll need to use them to calculate logs 
using properties
In the following problems I'll start by giving you a couple of 
log values. You'll need to use them to calculate logs 
using properties
Example)
log4(16) = 2
log4(64) = 3

In the following problems I'll start by giving you a couple of 
log values. You'll need to use them to calculate logs 
using properties
Example)
log4(16) = 2
log4(64) = 3Find
log4(4) 
In the following problems I'll start by giving you a couple of 
log values. You'll need to use them to calculate logs 
using properties
Example)
log4(16) = 2
log4(64) = 3
log4(4) = log4(64/16) = 
In the following problems I'll start by giving you a couple of 
log values. You'll need to use them to calculate logs 
using properties
Example)
log4(16) = 2
log4(64) = 3
log4(4) = log4(64/16) = log4(64) - log4(16) = 
In the following problems I'll start by giving you a couple of 
log values. You'll need to use them to calculate logs 
using properties
Example)
log4(16) = 2
log4(64) = 3
log4(4) = log4(64/16) = log4(64) - log4(16) = 3 - 2 = 1
Given:

log4(11) = 1.73    and     log4(8) = 1.5

Find log4(88)  
What operation could we use to get from 
8 & 11 to 88?
Exponent
Addition
Subtraction
Multiplication
Division
Hint: Since 88 is 11 times 8 use the properties to solve
log4(88) = 
Given:

log4(11) = 1.73    and     log4(8) = 1.5

Find log4(88)  
Given:
log5(60) = 2.54    and     log5(12) = 1.54
Find log5(5)  
Hint: How can I get 5 from 60 and 12?
Addition
Subtraction
Multiplication
Division
Exponent
Given:
log5(60) = 2.54    and     log5(12) = 1.54
Find log5(5)  
Hint: Since we use division, division is the same as 
subtracting the values.
log5(2)  = 
Given:
log7(5) = 0.83
Find log7(25) 
Hint: How can I get from 5 to 25?
Addition
Subtaction
Multiplication
Division
Exponent
Use the information given to solve, 
not a calculator or the problem will be rounded incorrectly
Hint: Use the exponent property to solve
Given:
log7(5) = 0.83
Find log7(25) =
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