Question

a vendor purchased bananas at rs 16 per dozen and sold them at 10 for rs 18. find his gain or loss per cent

Answer 1

Let the no of bananas be bought x 
so total cost price = 16x/12 = 4x/3
 
so total selling price 18x/10 = Rs 9x/5 

we see that Selling price is more than cost price so 

the gain percentage = (9x/5 - 4x/3)/4x/3 x 100 = 35 % ANSWER

Answer 2

Cp:
12 at  Rs16
each at Rs16/12=Rs.1.33

Sp:
10 for Rs 18
each for Rs 18/10=Rs 1.8

PRofit: Rs 0.47
profit %=0.47X100/1.33~=35%