A shopkeeper bought 25 kg. of pulses at the rate of Rs. 54 kg. He sold forty percent of the total quantity at the rate of Rs. 50 per kg. at what price per kg approximately should he sell the remaining quantity to make 25% overall profit?

Cost price = 25 kg × Rs. 54/kg = Rs. 1350. Target selling price for 25% profit = 1350 × 1.25 = Rs. 1687.50. First 40% (10 kg) sold at Rs. 50/kg = Rs. 500. Remaining 15 kg needs to be sold at (1687.50 - 500)/15 = Rs. 79 per kg. The key is to first calculate the total revenue needed for 25% profit, then subtract what's already earned from partial sales.