a man bought 12 oranges for 22.8 naira and sells 4 for 10 naira.what is his percentage gain

AAAaannndd the bot gets it wrong yet again!

4 for 10 naira = 2.5 naira each
2.5/1.9 = 1.315, for a 31.5% gain

The cost of one orange is 22.8/12 = 1.9 naira.

The selling price of four oranges is 10*4 = 40 naira.
The selling price of one orange is 40/4 = 10 naira.
The profit per orange is 10 - 1.9 = 8.1 naira.
The percentage gain is (8.1/1.9) * 100% = 426.32%.