Please!
A bottle of laundry detergent costs $3.60. Each bottle can be used to wash 23 loads of laundry.
$$Quantity\ A: \ $40 $$ $$\ Quantity\ B:$$ $$The\ approximate\ cost\ of\ the\ laundry\ detergent\ needed\ to\ wash\ 250\ loads\ of\ laundry$$
My argument: In real life we cannot purchase a fraction of a detergent bottle, so it has to be an integer. Consequently, the number of bottles needed $= 250/23$, which has to be rounded up to be $11$ bottles. The cost of $11$ bottles are $39.6$. So the approximate cost is $40 and both quantities are equal.
The book's argument: $$The\ cost\ per\ load =3.60/23 = $0.1565$$ $$Total\ cost= 250 *0.1565=$39.13 < Quantity\ A$$
Please advise, which argument is more correct?
This is not actually a mathematical problem. However I think which answer is the best depends on the class you are attending. In primary school the best one is the book's one. In the successive classes and on Quizzes and QI Test magazines (and for my personal taste) the best one is yours. Hope I helped