Multiple choice

A painter mixes blue paint with white paint so that the mixture contains 10% blue paint. In a mixture of 40 litres paint how many litres blue paint should be added so that the mixture contains 20% of blue paint ?

  1. 2.5

  2. 5

  3. 4.5

  4. 8
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Initial mixture has 4L blue (10% of 40L) and 36L white. Let x be blue added. New blue = 4+x, total = 40+x. We want (4+x)/(40+x) = 20% = 0.2. Solving: 4+x = 8 + 0.2x, so 0.8x = 4, giving x = 5L.

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