Answer:
he bought 10kg for 240Rs
cost price of 1kg= 240/10=24Rs
he sells 7kg for a gain of 210Rs
he sells the remaining 3kg of water price of 24Rs per kg = 3*24=72Rs
total gain: 210+72 = 282Rs
% gain: [(282-240)/240]*100=17.5%
he won a % of 17.5%
Explanation: