+12 Sheena is wrapping boxes using a roll of wall paper with a total area of 3.5 m2. Each box has a 20 cm width, 20 cm length, and 40 cm height. If Sheena uses 20% extra paper on each box, how many boxes can she wrap? Show your work.
+23246 Total surface area = 2·length·width + 2·length·height + 2·width·height
= 2·20·20 + 2·20·40 + 2·20·40 = 4000 cm2
Adding an extra 20%: 20% of 4000 = 800 ---> 4800 cm2
There are 10 000 cm2 in 1 m2, so there are 3.5 x 10 000 = 35 000 cm2 of wrapping paper.
35 000 cm2 / 4800 cm2 = 7.3 boxes = 7 boxes.
