in a school with 632 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 = ( 632 - x ) . then , ( 11 3 / 4 × 632 ) ⇔ 11 x + 12 ( 632 - x ) ⇔ x = 7584 - 7426 ⇔ 158 . answer d"
subtract(multiply(12, 632), multiply(add(11, divide(9, 12)), 632))