When an ice box is packed with 10 identical bottles of coke, it has a mass of 9.2 kg. When the ice box is packed with 20 identical packets of lemonade, it has a mass of 7.2 kg. A bottle of coke weighs 470 g more than a packet of lemonade. What is the mass of the empty ice box in kg?
1000 g = 1 kg
470 g = 470 ÷ 1000 = 0.47 kg

Mass of 1 packet of lemonade = 1 P
Mass of 1 bottle of coke = 1 P + 0.47

Mass of 20 packets of lemonade = 20 P
Mass of 10 bottles of coke = 10(1 P + 0.47) = 10 P + 4.7 

Ice Box + 10 P = 9.2 - 4.7 = 4.5
Ice Box + 10 P = 4.5 --- (1)

Ice Box + 20 P = 7.2 --- (2)

(2) - (1)
20 P - 10 P = 7.2 - 4.5 
10 P = 2.7

1 P = 2.7 ÷ 10 = 0.27

10 P = 10 x 0.27 = 2.7

Mass of the empty ice box
= 4.5 - 2.7
= 1.8 kg

Answer(s): 1.8 kg