CA Foundation · Quantitative Aptitude · Ratio and Proportion, Indices and Logarithms
If a : b = 2 : 3 and b : c = 4 : 5, then the value of (a + b) : (b + c) is:
The ratio is 20 : 27. Equalising b gives a : b : c = 8 : 12 : 15, so a + b = 20 and b + c = 27, hence (a + b) : (b + c) = 20 : 27.
- A20 : 27Correct
- B10 : 13
- C5 : 8
- D4 : 5
Explanation
Make b equal: a : b = 8 : 12 and b : c = 12 : 15, so a : b : c = 8 : 12 : 15. Then a + b = 20 and b + c = 27, giving 20 : 27. Option 5 : 8 wrongly adds the ratio terms without equating b.
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