Higher June 2018 Paper 6 Q2

OCRHigherCurrent spec4 marksPercentagesRatio & Basic Proportion

2 A box contains only red, blue and green pens.
The ratio of red pens to blue pens is 5 : 9.
The ratio of blue pens to green pens is 1 : 4.

Calculate the percentage of pens that are blue. [4]