Multiple choice

The ratio of the number of red pens in a bag to that of blue pens is 1 : 2. If 9 black pens are added, the ratio of the numbers of red, blue and black pens becomes 2 : 4 : 3. How many blue pens were in the bag

  1. 11

  2. 10

  3. 12

  4. 15

  5. N/A
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The ratio of red, blue and black pens is 2 : 4 : 3. The number of red, blue and black pens are 2x, 4x and 3x respectively. => 3 x = 9=> x = 3 Therefore the number of blue pens = 4 x = 4 x 3 = 12

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