a farmer spent $ 36 on feed for chickens and goats . he spent 40 % money on chicken feed , which he bought at a 20 % discount off the full price , and spent the rest on goat feed , which he bought at full price . if the farmer had paid full price for both the chicken feed and the goat feed , what amount would he have spent on the chicken feed and goat feed combined ?
"a farmer spent 40 % money on chicken feed , so he spent 0.4 * $ 36 = $ 14.4 on chicken feed , thus he spent the remaining 36 - 14.4 = $ 21.6 on goat feed . now , since he bought chicken feed at a 20 % discount then the original price of it was x * 0.8 = $ 14.4 - - > x = $ 18 therefore if the farmer had paid full price for both the chicken feed and the goat feed , then he would he have spent 18 + 21.6 = $ 39.6 . answer : d ."
add(multiply(36, divide(40, const_100)), 36)