When an ice box is packed with 10 identical bottles of coke, it has a mass of 9.7 kg. When the ice box is packed with 20 identical packets of lemonade, it has a mass of 7.5 kg. A bottle of coke weighs 440 g more than a packet of lemonade. What is the mass of the empty ice box in kg?
1000 g = 1 kg
440 g = 440 ÷ 1000 = 0.44 kg

Mass of 1 packet of lemonade = 1 P
Mass of 1 bottle of coke = 1 P + 0.44

Mass of 20 packets of lemonade = 20 P
Mass of 10 bottles of coke = 10(1 P + 0.44) = 10 P + 4.4 

Ice Box + 10 P = 9.7 - 4.4 = 5.3
Ice Box + 10 P = 5.3 --- (1)

Ice Box + 20 P = 7.5 --- (2)

(2) - (1)
20 P - 10 P = 7.5 - 5.3 
10 P = 2.2

1 P = 2.2 ÷ 10 = 0.22

10 P = 10 x 0.22 = 2.2

Mass of the empty ice box
= 5.3 - 2.2
= 3.1 kg

Answer(s): 3.1 kg