Question

Question #72fd4

Answer 1

The answer is 248.

We have an arithmetic sequence :

`u_1 = 52`
`u_(n+1) = u_n - 6`

`=> u_n = 52 + (n-1)*(-6) = 58 -6n`,

where `u_n` gives you the number of windows in a given floor `n`
(n = 1 = ground floor).

The sum of the windows for `n` floors is given by :

`s_n = u_1 + u_2 + u_3 + ... + u_n = n*(u_1+u_n)/2`.

If `n = 8` :

`s_8 = 8*(52+58-6*8)/2 = 8*62/2 = 8*31 = 248`.