Question 1204026
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Answer:  <font color=red size=4>248 windows</font>



Explanation


In some countries, the 1st floor is considered to be above the ground floor. 
However, I'll consider the ground floor to be the 1st floor.


Here's the long way to do it without needing any formulas
1st floor = 52 windows
2nd floor = 52-6 = 46 windows
3rd floor = 46-6 = 40 windows
4th floor = 40-6 = 34 windows
5th floor = 34-6 = 28 windows
6th floor = 28-6 = 22 windows
7th floor = 22-6 = 16 windows
8th floor = 16-6 = 10 windows
In total there are 52+46+40+34+28+22+16+10 = <font color=red>248 windows</font>


Typing all that into a calculator is fairly tedious. Luckily there's a faster method.
The sequence 52,46,34,... is arithmetic with
a1 = 52 = first term
d = -6 = common difference
From there we would write:
Sn = sum of the first n terms
Sn = (n/2)*(2*a1 + d*(n-1))
S8 = (8/2)*(2*52 - 6*(8-1))
S8 = <font color=red>248</font>


Here's another method.
The nth term of an arithmetic sequence is: an = a1 + d(n-1)
Plug in a1 = 52 and d = -6, and simplify, to get an = -6n+58
Plug in n = 8 to get a8 = 10 to show there are 10 windows on the 8th floor.
Then,
Sn = sum of the first n terms
Sn = (n/2)*(first + last)
Sn = (n/2)*(a1 + an)
S8 = (8/2)*(a1 + a8)
S8 = (8/2)*(52 + 10)
S8 = <font color=red>248</font>
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