C2 geometric q help.

Start with 2a = a/(1-r) and see if you can work it out from there

Thanks, i had that, but i solved it wrongly,

Well if we start with 2a = a/(1-r)
Divide by a and you get 2 = 1/(1-r)

From there you just simply rearrange it to get r

can you help with 1 more q please, thanks,

There are 400 deers in jan 08
the population grows by 10% per year, but 30 deer are culled at the end of each year.

How many deers will there be in jan 19?

a=400, r=1.1 and n=11

Apply the normal sum for a geometric series with those values

After that you need to account for the 30 lost at the end of each year. So 30 x 11 = 330 lost over the 11 years. Then you simply take 330 away from the value you got for your previous sum

its not the sum of the deers, its the amount of individual deers.

a=400, r=1.1 and n=11

Apply the normal sum for a geometric series with those values

After that you need to account for the 30 lost at the end of each year. So 30 x 11 = 330 lost over the 11 years. Then you simply take 330 away from the value you got for your previous sum

This doesn't work, you cannot take the deer away at the end as this would increase the number comming in each year e.g. if you have 1 and add 10% then minus 0.1 you will always have 1 but with your method you would get 1.01.