14) B

The key to answering this question is remembering that making a new colour requires equal amounts of other colours.

Brown requires equal quantities of red, yellow and green. Since the mural contains 30% brown, it must have 10% red, 10% yellow and 10% green. (equal amounts of all three colours make brown)

Green requires equal amount of blue and yellow. So there is 5% blue and 5% yellow extra. So far there is, 10% red, 15% yellow and 5% blue. We are also told there is extra 10% green (= 5% blue and 5% yellow)

So far = 10% red, 20% yellow, 10% blue

The mural also contains 20% red. Adding the initial 10% red in brown, there is a total of 30% red so far.

10% of blue
20% of yellow
10% of orange = 5% red and 5% yellow
10% of purple = 5% blue and 5% red
10% of green = 5% yellow and 5% blue

In total the mural contains:
Red = 10 + 20 + 5 + 5 = 40%
Yellow = 20 + 5 + 5 = 30%
Blue = 10 + 10 + 5 + 5 = 30%

Since 20ml of red is left, 80ml was used (there was initially 100ml of each colour).

40% = 80ml
1% = (80÷40) = 2ml
100% = 2 x 100 = 200ml
The mural contains 200ml of total colours.

Since the mural has 30% blue, amount of blue used = 0.3 x 200 = 60ml

Amount of blue left = 100 ml – 60 ml = 40 ml

2 thoughts on “2015 Section 1 Question 14

  1. The answer should be 40ml since the mural contains 20% blue. Therefore, the amount of blue = 0.2×200= 40ml which is option B.

    1. Hi, thanks for pointing out the mistake! I have corrected it now. Upon recalculating, I realised that the mural contains 30% blue. Since the total quantity of colour used is 200 ml, amount of blue used = 30% of 200 ml = 60 ml. We have been asked to calculate the amount of blue left.

      Since we are told that the artist has 100 ml of each paint, and we know that we have used 60 ml, amount of blue left = 100 – 60 = 40 ml

      Again, I apologise for the mistake. I made a mistake somewhere in the calculation but I have corrected it now. Hope this helped. If you require any further help, please comment here (or on any other question) or contact me via our contact form. All the best!

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