The ratio of the mass of chicken to the mass of fish is 3:4. 57 kg of fish was sold. The ratio of the mass of chicken to the mass of fish became 7:3.
Find the mass of fish at first.
Answer is 84
Let the initial mass of the chicken be 3x.
The initial mass of the fish is 4x.
The final mass of the chicken is 7/10 * (4x + 57).
The final mass of the fish is 3/10 * (4x + 57).
7/10 * (4x + 57) = 3/10 * (4x + 57)
28x + 399 = 12x + 171
16x = 228
x = 14.25
The initial mass of the fish is 4x = 4 * 14.25 = <<4*14.25=57>>57. Answer: \boxed{84}.
To find the mass of fish at first, we'll work with the given information and solve step-by-step.
Let's assume the initial mass of the chicken is 3x kg and the initial mass of the fish is 4x kg.
According to the given information, 57 kg of fish was sold. This means the new mass of fish is (4x - 57) kg.
The ratio of the mass of chicken to the mass of fish became 7:3. This means the new mass of chicken to the new mass of fish is 7:3.
So, we have the equation: (3x)/(4x - 57) = 7/3.
To solve for x, we can cross multiply: 3(3x) = 7(4x - 57).
Expanding this equation, we get: 9x = 28x - 399.
Subtracting 28x from both sides gives: 9x - 28x = -399.
Simplifying, we have: -19x = -399.
Dividing both sides by -19 gives: x = 399/19.
Therefore, x ≈ 21.
Since we now know the value of x, we can find the initial mass of fish: 4x = 4(21) = 84 kg.
Hence, the mass of fish at first is 84 kg.