A rucksack containing three bottles weighs 1.8 kg.
Each water bottle weighs the same and the empty rucksack weighs 300 g.
How much does one water bottle weigh?
Let's assume the weight of each water bottle is x kg.
The weight of the rucksack without the bottles is 300 g, which is equal to 0.3 kg.
Therefore, the weight of the three water bottles is 1.8 kg - 0.3 kg = 1.5 kg.
Since each water bottle weighs the same, we can divide the total weight by the number of bottles to find the weight of one water bottle.
1.5 kg / 3 = 0.5 kg.
So, one water bottle weighs 0.5 kg.
To find the weight of one water bottle, we need to subtract the weight of the empty rucksack from the total weight of the rucksack with the bottles.
Total weight of the rucksack with three bottles = 1.8 kg
Weight of the empty rucksack = 0.3 kg
Weight of the three bottles = Total weight of the rucksack with three bottles - Weight of the empty rucksack
= 1.8 kg - 0.3 kg
= 1.5 kg
Since there are three bottles, the weight of a single water bottle can be found by dividing the total weight of the three bottles by the number of bottles.
Weight of one water bottle = Weight of the three bottles / Number of bottles
= 1.5 kg / 3
= 0.5 kg
Therefore, one water bottle weighs 0.5 kg.