CA Foundation · Quantitative Aptitude · Ratio and Proportion, Indices and Logarithms
If (3x + 2y)/(3x − 2y) = 7/3, then the value of x/y is:
Componendo and dividendo give 3x/2y = (7 + 3)/(7 − 3) = 5/2. Hence x/y = (5/2)×(2/3) = 5/3. Check: with x = 5, y = 3, (15 + 6)/(15 − 6) = 21/9 = 7/3, which matches.
- A5/3Correct
- B3/5
- C5/6
- D10/3
Explanation
Componendo-dividendo gives 6x/4y = (7 + 3)/(7 − 3) = 10/4 = 5/2. So 6x/(4y) = 5/2, i.e. x/y = (5/2)×(4/6) = 5/3. Option 5/6 forgets the 4/6 factor partly, and 10/3 comes from using 10/4 wrongly.
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