The pressure created by the water at the bottom of the lake is 4MPa. The density of water is 1000 kg / m3.

The pressure created by the water at the bottom of the lake is 4MPa. The density of water is 1000 kg / m3. If atmospheric pressure is not taken into account, the depth of the lake is …

The water pressure at the bottom of the lake can be expressed in the formula:
P = ρ * g * h, where P is the pressure created by water at the bottom of the lake (P = 4 MPa = 4 * 10 ^ 6 Pa), ρ is the density of water in the lake (we take ρ = 1000 kg / m ^ 3), g is the acceleration of gravity (we take g = 10 m / s ^ 2), h is the depth of the lake.
Let’s express and calculate the depth of the lake:
h = P / ρ * g = (4 * 10 ^ 6) / (1000 * 10) = 4 * 10 ^ 2 = 400 m.
Check: m = Pa / ((kg / m ^ 3) * m / s ^ 2) = (kg / m * s ^ 2) / (kg / (m ^ 2 * s ^ 2)) = m.
Answer. The depth of the lake is 400 m.