How many kg of pure salt must be added to a 40 kg of 4 % solution of salt and…
2024
How many kg of pure salt must be added to a 40 kg of 4 % solution of salt and water to increase it to a 10 % solution
- A.
2.0 kg
- B.
2.44 kg
- C.
2.8 kg
- D.
2.66 kg
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Correct answer: D
Answer: 2.66 kg (exact value 8/3 kg = 2.666...)
Work:
Amount of salt initially = 4% of 40 kg = 0.04 × 40 = 1.6 kg.
Let x kg of pure salt be added. The new concentration should be 10%:
(1.6 + x) / (40 + x) = 0.10
Multiply both sides: 1.6 + x = 0.1(40 + x) = 4 + 0.1x.
Rearrange: x − 0.1x = 4 − 1.6 ⇒ 0.9x = 2.4.
Solve: x = 2.4 / 0.9 = 8/3 = 2.666...
Therefore, about 2.67 kg of pure salt is required. The given option 2.66 kg is a close rounded value of the exact answer 2.666... kg.