In what ratio must rice at Rs. 60 per kg is mixed with rice at Rs. 90 per kg so that the mixture be worth Rs. 80 per kg?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → 1:2
By the rule of alligation:
\( \displaystyle \frac{\text{Cheaper}}{\text{Dearer}} = \frac{\text{Dearer price} - \text{Mean price}}{\text{Mean price} - \text{Cheaper price}} \)
\( \displaystyle \frac{\text{Cheaper}}{\text{Dearer}} = \frac{90 - 80}{80 - 60} = \frac{10}{20} = \frac{1}{2} \)
So the rice at Rs. 60 and the rice at Rs. 90 are mixed in the ratio 1 : 2. Check: 1 kg at Rs. 60 and 2 kg at Rs. 90 cost Rs. 240 for 3 kg, which is Rs. 80 per kg.