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The number which when subtracted from each term of the ratio 19 : 31 reduces it to 1 : 4 is
A12
B1
C15
D5
Answer & Solution
Correct answer: C. 15
1. Let the number be x; set up (19 - x)/(31 - x) = 1/4.
2. Cross-multiply: 4(19 - x) = (31 - x), so 76 - 4x = 31 - x.
3. 76 - 31 = 4x - x = 3x, so 3x = 45.
4. x = 15.
_Source: ICAI BoS Foundation Paper 3, Ch 1 Unit I 'Ratio', p.5 Ex.1(A) Q23_
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