Question

If pens are brought at Rs48 per dozen and sold at 3 for Rs 15 the total profit on 5.5 dozen is

Answer 1

cost price,
1 dozen =12 pen =48rupee
1pen=48/12=4rupee
5.5 dozen=66*4=264 rupee

5.5dozen=5.5*12=66 pens

selling price,
3 sold =15rupee
1sold =15/3=5 rupee
66 sold at=66*5=330 rupee

Here person or shopkeeper has loss not profit.
so,
loss=SP-CP
loss=330-264
loss=64 rupee
which is required answer.