A trader while buying take 60% extra but while selling gives 60% less he claims to make 39% profit on this transaction find the actual percentage gain made by the trader do it without an equation

The answer is 456%.If it is correct then here is how I got it, CP of 1 kg is 100/-.And he get 60% extra therefore gets 1.6kg -.> 100/- SP after 39% profit margni is 139 for 0.4kg(Since he gives 60% less,he would initially sell the from the 1 kg and not the 1.6kg) 139 ->0.4Kg Get both CP and SP on same platform CP -> Rs.100 - 1.6Kg SP -> Rs.139 - 0.4Kg SP of 1.6Kg using unitary method will give 556. Profit(%) = (556-100)/100*100 = 456%