in a school with 604 students , the average age of the boys is 12 years and that of the girls is 11 years . if the average age of the school is 11 years 9 months , then the number of girls in the school is
"sol . let the number of grils be x . then , number of boys = ( 600 - x ) . then , ( 11 3 / 4 × 604 ) ⇔ 11 x + 12 ( 604 - x ) ⇔ x = 7248 - 7097 ⇔ 151 . answer b"
subtract(multiply(12, 604), multiply(add(11, divide(9, 12)), 604))