To determine the profit percentage, follow these steps:
- First, calculate the marked price (M.P.) of the item. The item is marked 50% higher than its cost price (C.P.):
$$M.P. = C.P. + 0.50 \times C.P. = 1.50 \times 600 = 900$$
- Next, compute the selling price (S.P.) after the discount. A 20% discount is allowed on the marked price:
$$S.P. = M.P. - 0.20 \times M.P. = 0.80 \times 900 = 720$$
- Now calculate the profit made by the shopkeeper. The profit is the difference between the selling price and the cost price:
$$\text{Profit} = S.P. - C.P. = 720 - 600 = 120$$
- Finally, find the profit percentage using the formula:
$$\text{Profit Percentage} = \left(\frac{\text{Profit}}{\text{C.P.}} \right) \times 100 = \left(\frac{120}{600} \right) \times 100= 20\%$$
Therefore, the shopkeeper's profit percentage is 20%.