Answer:
D. 750(0.75)ˣ
Step-by-step explanation:
Let the new brightness be L'. Since our initial brightness L₀ reduces by 25 %, we have that L' = L₀ - 25% of L₀
L' = L₀ - 0.25L₀
L' = 0.75L₀
Adding the second screen, the new intensity is L" = L' - 25 % of L'
L" = L' - 0.25 L'
L" = 0.75L'.
Since L' = 0.75L₀,
L" = 0.75L' = 0.75(0.75L₀) = 0.75²L₀
Adding the third screen, the new intensity is L"' = L'' - 25 % of L''
L'" = L" - 0.25 L"
L"' = 0.75L".
Since L" = 0.75L' = 0.75²L₀
L"' = 0.75L" = 0.75(0.75²L₀) = 0.75³L₀
So, we see a pattern here.
The intensity after x screens is L = (0.75)ˣL₀
Since L₀ = 750 lumens,
L = 750(0.75)ˣ
