Volume (cm3) Surface Area (cm2) 6.4 Economy of Design Volume (cm3) Surface Area (cm2) Container # 1 2000 1500 Container # 2 2000 500 Container # 3 2000 1000 The above are potential containers to be used by a company for a new product. Which one do you think the boss might like to use? Why? What other factors might influence the decision? A # is often used to show how the volume compares to the surface area. It is called the ECONOMY RATE – a rate (a # that compares 2 quantities) that compares the volume of a container to its surface area. E.R. = volume surface area

6.4 Economy of Design The higher the economy rate …… the more economical the larger the volume in relation to the surface area The lower the economy rate …… the less economical the smaller the volume in relation to the surface area Determine the economy rate for the containers above. #1 E.R. = V = 2000 = 1.33 S.A 1500 #2 E.R. = V = 2000 = 4 S.A 500 #3 E.R. = V = 2000 = 2 S.A 1000 Therefore #2 is the most economical, its volume is 4 times its surface area.