The jar contains 4 kg of kerosene. How many kilograms of water are included in the same jar?

Given:

m kerosene = 4 kg;

p kerosene = 800 kg / m³;

p water = 1000 kg / m³;

m water =?

Solution.

Since in the condition of the problem one and the same bank is considered, the volume of which does not change, the volume for kerosene and for water will be the same. If you find the volume of incoming kerosene, then you can find the mass of water.

From the density formula p = m / V we express V:

V = m / p.

Find V kerosene:

V kerosene = m kerosene / p kerosene = 4 kg / 800 kg / m³ = 0.005 m³.

Now, from the same original formula for the density, we express the mass:

m water = p water * V water.

Since V kerosene = V water, we substitute the values ​​into the formula:

m of water = 1000 kg / m³ * 0.005 m³ = 5 kg.

Answer: 5 kg.