Question

ach light bulb at Hotel California is either incandescent or fluorescent. At a certain moment, forty percent of the incandescent bulbs are switched on, and ninety percent of the fluorescent bulbs are switched on. If eighty percent of all the bulbs are switched on at this moment, what percent of the bulbs that are switched on are incandescent

Answer 1

10%

Explanation:

The computation of the percentage of bulbs that switched on incandescent is as follows;

Let us assume the incandescent be I

And, the fluorescent be F

Now the equation is

0.4I + 0.9F = 0.8 (I+F)

0.41I + 0.9F = 0.8I + 0.8F

So here

0.4I = 0.1F

Now the percentage would be for incandescent in the case of switched on is

= 0.4I ÷ 0.8(I+F) × 100

= 0.1F ÷ 1F

= 10%