Series and Sequence question (1 Viewer)

[dabatman]

Hi,

Can anyone please help me solve these two questions from Maths in Focus?

Thanks

 

[fan96]

The question is somewhat ambiguously worded but I will assume the meaning to be "decreasing by 5% of the previous year's population".

Use the formula for geometric sequences.

Let be the population, expressed as a percentage of the original, at the start of the ^th year (be careful with wording).





(decreasing by 5% is the same as taking 95%)

You can do the first question with simple substitution. The other two can be done with a substutition and then rearranging to make the subject (logarithms will be required).

 

[dabatman]

Thank you