An appliance dealer sold a washing machine and a dryer together. Charging 15% profit on the machine and 20% on the dryer, he made ₹5400. Had he charged 20% on the machine and 15% on the dryer instead, he would have made ₹5100. The washing machine cost him (in ₹):

With costs $w$ and $d,0.15w+0.20d=5400$ and $0.20w+0.15d=5100$. Adding: $0.35(w+d)=10500$ → $w+d$ = ₹30000. Subtracting: $0.05(d-w)=300$ → $d-w$ = ₹6000. So the dryer cost ₹18000 and the machine ₹12000. (Check: 1800 + 3600 = ₹5400 and 2400 + 2700 = ₹5100.) ₹18000 is the dryer's cost, and simply halving the ₹30000 total assumes the two items cost the same, which the ₹300 gap between the two profit figures rules out.