Problem: the average age of 35 students in a class is 16 years . the average age of 21 students is 14 . what is the average age of remaining 7 students ?
Rationale: "solution sum of the ages of 14 students = ( 16 x 35 ) - ( 14 x 21 ) = 560 - 294 . = 266 . ∴ required average = 266 / 7 = 38 years . answer d"
annotated_formula: subtract(add(add(multiply(35, 16), 21), 35), multiply(35, 16))