Logarithms 3

1
Logarithms (3)

• Calculators and logs
• Logarithmic equations

2
Using your calculator
The log key on your calculator works out logs to
base 10.
What would you expect your calculator output if
you input the following
Log(100) Log(1000) Log(1)
3
Solving log equations
Solve 3x 35
For convenience we use log10
Take log of both sides
Using log laws
Re-arrange
Using your calculator
4
Solving log equations
Solve 53x7 89
Take log of both sides
Using log laws
Re-arrange
Using your calculator
Solving
5
Activity 1
Time allowed 5 minutes
Solve the following..
x 2.23 x 3.13 x -0.54
5x 36 102x-5 18 43x1 5x
6
Activity 2
Time allowed 5 minutes
I earn 3 interest on my savings per year. How
long will it take for me to double my savings?
7
Activity 3
Time allowed rest of lesson
Turn to page 113 of your core 2 book and answer
questions in Exercise D.