Problem: the average weight of a class of 24 students is 35 kg . if the weight of the teacher be included , the average rises by 400 g . the weight of the teacher is :
Rationale: weight of the teacher = ( 35.4 x 25 - 35 x 24 ) kg = 45 kg . answer : a
annotated_formula: subtract(multiply(add(35, divide(400, const_1000)), add(24, const_1)), multiply(24, 35))