Calculate how much fresh water needs to be added to 10 kg of seawater to reduce the salt content by 2.5 times?

1.ω_1 / ω_2 = 2.5
2.ω_1 = m_salt / m_ (sea water) = m_salts / 10
3. Let the mass of fresh water be X g, then
ω_2 = m_salts / (m_ (sea water) + X) = m_salts / (10 + X)
4.2.5 = m_salt / 10 ∶ m_salts / (10 + X)
Hence X = 15 kg
Answer: 15 kg

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