?$ 2.4m=240\ \mathrm {cm},$??$3.2m=320\ \mathrm {cm}$?
?$ $?廚房地面面積為?$320×240 = 76800(\mathrm {cm}^2)$?
?$ A$?種地磚:?$76800\div (80×80)×150 = 1800($?元?$)$?
?$ B$?種地磚:?$76800\div (60×60)≈22($?塊?$)$?
?$80×22 = 1760($?元?$)$?
?$ C$?種地磚:?$76800\div (40×40)×40 = 1920($?元?$)$?
?$ 1920>1800>1760$?
答:選擇?$B$?種地磚最便宜。