arithmetic sequence

[red and white kop!]

i though this would be pretty straightforward

an employee starts work on an annual salary of $30 000. His pay scale will give him an increase of $800 per annum on 1 January until 1 January 2015 inclusive. He remains on this salary until he retires on 31 December 2040. How much will he earn during his working life?

ok so the sum of the first 15 years is 0.5n(2a+d(n-1)) = 7.5 (60000 + 800 x 14) = 534 000
his final salary l = a+d(n-1) = 41 200
he will earn this every year for 25 years.
so he will earn on total 534 000 + (41 200 x 25)
=1 564 000

this is wrong
the real answer is $1 626 000
how do i get to that? where is the mistake in my calculations?

 

[Denis]

http://www.mathhelpforum.com/math-help/ ... 57697.html

 

[red and white kop!]

whats your point?
btw the starting date is 1 jan 2000, i forgot that, the mhf guys pointed it out

 

[Denis]

Jan1/00 to Jan1/15 = 16 years, not 15; your sum to Jan 1/15 is 576,000, final salary 42,000;
576,000 + 42,000*25 = 1,626,000.

 

[Deleted member 4993]

whats your point?

The point is - we (the volunteers) don't waste our time if it is being explained in another forum.

 

[Denis]

Thanks, Subhotosh; you may now vacate the corner...

 

[red and white kop!]

why dont you try doing it first then? or if you dont want to then you dont have to post a thing
theres nothing wrong with trying to get all the help i can

 

[mmm4444bot]

why dont you try doing it first then?

Because it's not a bloody race, mate. :|

 

[Denis]

why dont you try doing it first then?

Ahhhh I see: YOU will post your homework problems and WE will rush to solve them...GOOD IDEA!!

 

[red and white kop!]

i dont see why you are getting all defensive, i just want help, if you dont want to give it well i can't force you can i

 

[galactus]

Since it is inclusive, you must count the year it begins as well. Which gives 16 raises instead of 15. 16/2=8.

\(\displaystyle 8(60000+15(800))+25(15*800+30000)\)