When an ice box is packed with 10 identical bottles of coke, it has a mass of 8.5 kg. When the ice box is packed with 15 identical packets of lemonade, it has a mass of 3.6 kg. A bottle of coke weighs 550 g more than a packet of lemonade. What is the mass of the empty ice box in kg?
1000 g = 1 kg
550 g = 550 ÷ 1000 = 0.55 kg

Mass of 1 packet of lemonade = 1 P
Mass of 1 bottle of coke = 1 P + 0.55

Mass of 15 packets of lemonade = 15 P
Mass of 10 bottles of coke = 10(1 P + 0.55) = 10 P + 5.5 

Ice Box + 10 P = 8.5 - 5.5 = 3
Ice Box + 10 P = 3 --- (1)

Ice Box + 15 P = 3.6 --- (2)

(2) - (1)
15 P - 10 P = 3.6 - 3 
5 P = 0.6

1 P = 0.6 ÷ 5 = 0.12

10 P = 10 x 0.12 = 1.2

Mass of the empty ice box
= 3 - 1.2
= 1.8 kg

Answer(s): 1.8 kg