Multiple choice

In a chemical laboratory, a scientist is working with two solutions, A and B. Solution A contains 30% of Chemical X, and Solution B contains 50% of Chemical X. The scientist needs to create a mixture with 40% of Chemical X. If the scientist mixes 5 litres of Solution A with 3 litres of Solution B, then how much more of Chemical X (in litres) should be added to achieve this concentration in the mixture?

  1. 1 litre

  2. 1 2 litre

  3. 1 3 litre

  4. 1 4 litre

  5. 1 5 litre
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Solution A contributes 5 x 0.30 = 1.5 litres of Chemical X, and Solution B contributes 3 x 0.50 = 1.5 litres. The mixture initially contains 3 litres of X in 8 litres, or 37.5%. If x litres of pure X are added, (3 + x)/(8 + x) = 0.40, giving x = 1/3 litre.

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