Problem: it will take 16 days for mary to complete a certain task alone . she worked for 8 days before she was joined by her sister . both of them completed the remaining task in 2 and half days . if her sister had joined her when she started the task , how many days would it have taken ?
Rationale: explanation : mary and her sister complete half work in 2.5 days = > they can complete whole work in 5 days answer : option d
annotated_formula: add(divide(divide(const_1, 8), divide(const_1, 16)), const_3)