In what ratio must pulses at Rs. 72 per kg be mixed with pulses Rs. 90 per kg so that the mixture be worth Rs. 80 per kg?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 5 : 4
By the rule of alligation,
\( \displaystyle \frac{\text{Quantity of cheaper}}{\text{Quantity of dearer}} = \frac{\text{Price of dearer} - \text{Mean price}}{\text{Mean price} - \text{Price of cheaper}} \)
\( \displaystyle = \frac{90 - 80}{80 - 72} = \frac{10}{8} = \frac{5}{4} \)
So the pulses at Rs. 72 and Rs. 90 per kg are mixed in the ratio 5 : 4.
Check: \(5 \times 72 + 4 \times 90 = 360 + 360 = 720\), and \(720 \div 9 = 80\) per kg.