In what ratio must sugar at Rs. 12 per kg be mixed with sugar at Rs. 20 per kg so that the mixture is worth Rs. 15 per kg?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 5:3
By the rule of alligation:
\( \displaystyle \frac{\text{Quantity of cheaper}}{\text{Quantity of dearer}}=\frac{\text{Dearer price}-\text{Mean price}}{\text{Mean price}-\text{Cheaper price}} \)
\( \displaystyle =\frac{20-15}{15-12} \)
\( \displaystyle =\frac{5}{3} \)
So the sugar at Rs. 12 and the sugar at Rs. 20 are mixed in the ratio 5 : 3.
Check: 5 kg at Rs. 12 and 3 kg at Rs. 20 cost 60 + 60 = Rs. 120 for 8 kg, i.e. Rs. 15 per kg.