In what ratio must lentils costing ₹46 per kg be mixed with lentils costing ₹71 per kg, so that the mixture is worth ₹67 per kg?

💡 Solution & Explanation

Use alligation: the cheaper part : the dearer part = (dearer price − mixture price) : (mixture price − cheaper price) = (71 − 67) : (67 − 46) = 4 : 21, which simplifies to 4 : 21. Check: mixing in that ratio gives an average of ₹67 per kg. Writing the differences the other way round is the most common mistake.