each light bulb at a hotel is either incandescent or fluorescent . at a certain moment , forty percent of the incandescent bulbs are switched on , and eighty percent of the fluorescent bulbs are switched on . if 75 percent of all the bulbs are switched on at this moment , what percent of the bulbs that are switched on are incandescent ?
"let i be the number of incandescent bulbs . let f be the number of fluorescent bulbs . 0.4 i + 0.8 f = 0.75 ( i + f ) 0.05 f = 0.35 i f = 7 i this means that for every 1 incandescent bulb , there are 7 fluorescent bulbs . the percent of bulbs that are switched on which are incandescent is : 0.4 i / ( 0.4 i + 0.8 f ) = 0.4 i / ( 0.4 i + 0.8 * 7 i ) = 0.4 i / 6 i = 1 / 15 which is about 6.7 % . the answer is a ."
divide(multiply(subtract(const_100, 75), multiply(add(divide(const_2, const_0_25), const_2), const_4)), const_100)