When an ice box is packed with 15 identical bottles of soda, it has a mass of 11.25 kg. When the ice box is packed with 30 identical packets of milo, it has a mass of 7.5 kg. A bottle of soda weighs 460 g more than a packet of milo. What is the mass of the empty ice box in kg?
1000 g = 1 kg
460 g = 460 ÷ 1000 = 0.46 kg

Mass of 1 packet of milo = 1 P
Mass of 1 bottle of soda = 1 P + 0.46

Mass of 30 packets of milo = 30 P
Mass of 15 bottles of soda = 15(1 P + 0.46) = 15 P + 6.9 

Ice Box + 15 P = 11.25 - 6.9 = 4.35
Ice Box + 15 P = 4.35 --- (1)

Ice Box + 30 P = 7.5 --- (2)

(2) - (1)
30 P - 15 P = 7.5 - 4.35 
15 P = 3.15

1 P = 3.15 ÷ 15 = 0.21

15 P = 15 x 0.21 = 3.15

Mass of the empty ice box
= 4.35 - 3.15
= 1.2 kg

Answer(s): 1.2 kg