When an ice box is packed with 25 identical bottles of coke, it has a mass of 17.1 kg. When the ice box is packed with 30 identical packets of lemonade, it has a mass of 7.9 kg. A bottle of coke weighs 410 g more than a packet of lemonade. 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 lemonade = 1 P
Mass of 1 bottle of coke = 1 P + 0.41

Mass of 30 packets of lemonade = 30 P
Mass of 25 bottles of coke = 25(1 P + 0.41) = 25 P + 10.25 

Ice Box + 25 P = 17.1 - 10.25 = 6.85
Ice Box + 25 P = 6.85 --- (1)

Ice Box + 30 P = 7.9 --- (2)

(2) - (1)
30 P - 25 P = 7.9 - 6.85 
5 P = 1.05

1 P = 1.05 ÷ 5 = 0.21

25 P = 25 x 0.21 = 5.25

Mass of the empty ice box
= 6.85 - 5.25
= 1.6 kg

Answer(s): 1.6 kg