When an ice box is packed with 25 identical bottles of soda, it has a mass of 15.55 kg. When the ice box is packed with 40 identical packets of milo, it has a mass of 6.6 kg. A bottle of soda weighs 430 g more than a packet of milo. What is the mass of the empty ice box in kg?
1000 g = 1 kg
430 g = 430 ÷ 1000 = 0.43 kg

Mass of 1 packet of milo = 1 P
Mass of 1 bottle of soda = 1 P + 0.43

Mass of 40 packets of milo = 40 P
Mass of 25 bottles of soda = 25(1 P + 0.43) = 25 P + 10.75 

Ice Box + 25 P = 15.55 - 10.75 = 4.8
Ice Box + 25 P = 4.8 --- (1)

Ice Box + 40 P = 6.6 --- (2)

(2) - (1)
40 P - 25 P = 6.6 - 4.8 
15 P = 1.8

1 P = 1.8 ÷ 15 = 0.12

25 P = 25 x 0.12 = 3

Mass of the empty ice box
= 4.8 - 3
= 1.8 kg

Answer(s): 1.8 kg