Lights on.. lights off

[dumb.doofus]

Eighty percent of the lights at Hotel California are switched on at 8 p.m. one evening. However, forty percent of the lights that are supposed to be switched off are actually switched on, and ten percent of the lights that are supposed to be switched on are actually switched off. What percent of the lights that are switched on are supposed to be switched off?

22(2/9)%
16(2/3)%
11(1/9)%
10%
5%

[scoobydooby]

am getting 10%

set it up in a 2 by 2 matrix.
let total lights be 100, 80 actually switched on, 20 actually switched off.
let x be expected to be switched off, 100-x expected to be switched on.

0.4x+0.9(100-x)=80.....1
solving we get x=20

expected to be off/actually on=0.4*20/80=10%

hence, D

[Svedankae]

what would that 2x2 matrix for yours look like?

[scoobydooby]

here you go

[dumb.doofus]

Well done, ScoobyDooby..