Problem: the mean of 50 observations was 36 . it was found later that an observation 48 was wrongly taken as 23 . the corrected new mean is :
Rationale: "correct sum = ( 36 * 50 + 48 - 23 ) = 1825 . correct mean = 1825 / 50 = 36.5 answer a"
annotated_formula: divide(add(multiply(36, 50), subtract(subtract(50, const_2), 23)), 50)