The mass of one liter of seawater is 1kg 25g. What is the mass of 4 liters of water?

To solve this problem, we will use the proportioning. Let’s denote by x the mass of water.
Let’s make the following proportion:
1 liter = 1 kg 25 g;
4 liters = x;
Let’s solve this proportion using the method of diagonals, multiplying each diagonal with each other.
1 * x = 1 kg 25 g * 4;
Let’s sort this equation by performing the possible multiplication actions:
1 * x = 4 kg 100 g;
Find x:
x = 4 kg 100 g.
This means that the mass of water is 4 kg 100 g.
Answer: 4 kg 100 g.