Ratio of new score to original score

CAT 2018 Slot 2 · QA · Medium · Ratios

The scores of Amal and Bimal in an examination are in the ratio 11 : 14. After an appeal, their scores increase by the same amount and their new scores are in the ratio 47 : 56. The ratio of Bimal's new score to that of his original score is

  1. A.

    3 : 2

  2. B.

    4 : 3

  3. C.

    5 : 4

  4. D.

    8 : 5

Answer

B

Explanation

Let original scores of Amal and Bimal be 11x11x and 14x14x. Let the increase in score for each be kk. New ratio: 11x+k14x+k=4756\frac{11x + k}{14x + k} = \frac{47}{56}.

Cross-multiplying: 56(11x+k)=47(14x+k)56(11x + k) = 47(14x + k) 616x+56k=658x+47k616x + 56k = 658x + 47k 9k=42x    k=143x9k = 42x \implies k = \frac{14}{3}x

Bimal's original score =14x= 14x. Bimal's new score =14x+k=14x+143x=563x= 14x + k = 14x + \frac{14}{3}x = \frac{56}{3}x.

Ratio of Bimal's new score to original score =563x14x=5642=43=4:3= \frac{\frac{56}{3}x}{14x} = \frac{56}{42} = \frac{4}{3} = 4 : 3.

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