# Total Cost calculation

Theresa bought lunch for herself and 2 friends. The cost for each lunch was between $3.95 and$4.80, including tax. Which of the following could be the total cost of the lunches that Theresa bought? A $9 B$13 C $18 D$26 Is the answer to the question above question $13 Total Cost(TC) = Average cost(AC) * Quantity (Q) = ( 3.95 + 4.8)/2 * 3 =13.125 How best can I explain the answer in a simple format to a grade 7 class? • July 24th 2011, 02:49 PM pickslides Re: Total Cost calculation Not sure if this will make things more confusing or not. Let $x$ be the cost of one lunch, we know $3.95 and there are 3 lunches in total so $3\times 3.95<3x<3\times 4.80$ $11.85<3x<14.4$ therefore the total cost must be$13 as none of the other options fit within the inequality.