When an ice box is packed with 10 identical bottles of 100 plus, it has a mass of 9.2 kg. When the ice box is packed with 15 identical packets of milk, it has a mass of 6.3 kg. A bottle of 100 plus weighs 410 g more than a packet of milk. What is the mass of the empty ice box in kg?
1000 g = 1 kg
410 g = 410 ÷ 1000 = 0.41 kg

Mass of 1 packet of milk = 1 P
Mass of 1 bottle of 100 plus = 1 P + 0.41

Mass of 15 packets of milk = 15 P
Mass of 10 bottles of 100 plus = 10(1 P + 0.41) = 10 P + 4.1 

Ice Box + 10 P = 9.2 - 4.1 = 5.1
Ice Box + 10 P = 5.1 --- (1)

Ice Box + 15 P = 6.3 --- (2)

(2) - (1)
15 P - 10 P = 6.3 - 5.1 
5 P = 1.2

1 P = 1.2 ÷ 5 = 0.24

10 P = 10 x 0.24 = 2.4

Mass of the empty ice box
= 5.1 - 2.4
= 2.7 kg

Answer(s): 2.7 kg