If the ratio of marks obtained by Ankit in the internals of all three subjects (Economics, Finance and Accounts) in that order is 9:3: 4, then what was the ratio of marks scored by Sachin in the externals of those three subjects in the same order?
Options:
A .  
18 : 10 : 5
B .  
3 : 1 : 2
C .  
17 : 51 : 67
D .  
24 : 45 : 30
Answer: Option D : D Let the total marks scored by the six students in Economics, Finance and Accounts be x, y and z respectively. ∴The ratio of marks scored by Ankit in the Internals of these papers would be: (30% of 10% of x) : (10% of 5% of y) : (10% of 10% of z) which would be the same as (0.03x): (0.005y) : (0.01z) = (3x) : (0.5y) : (z) But, (3x) : (0.5y) : (z) is equal to 9 : 3 : 4. ∴ 3x = 9, 0.5y = 3 and z = 4 ∴ The ratio x : y : z would be equal to 3 : 6 : 4. The marks scored by Sachin are 30%, 25%, and 25%, the ratio of marks would be 90 : 150 : 100, i.e. 9 : 15 : 10. Now, the marks scored by Sachin in Internals are 20%, 10% and 10%. ∴ Marks scored by him in Externals will be 80%, 90% and 90%. ∴ The required ratio would be (80% of 9) : (90% of 15) : (90% of 10), i.e. (7.2) : (13.5) : (9) This ratio would be equal to 72 : 135 : 90 or 24 : 45 : 30
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