A shopkeeper sells watermellon at profit of 10% but cheats to the extent of 10% while measuring Find profit %.

Answer

To solve the problem, we need to find the effective profit percentage of the shopkeeper who sells watermelons at a 10% profit but cheats by measuring only 90% of the actual weight. Let's break it down step by step.

### Step 1: Understanding the Selling Price (SP) and Cost Price (CP)
- Let's assume the Cost Price (CP) of 100 grams of watermelon is ₹100.
- Since the shopkeeper sells at a profit of 10%, the Selling Price (SP) for 100 grams will be:
\[ SP = CP + (10\% \text{ of } CP) = 100 + 10 = ₹110 \]

### Step 2: Calculating the Actual Weight Sold
- The shopkeeper cheats by measuring only 90% of the actual weight. So, instead of giving 100 grams, he gives:
\[ \text{Actual weight sold} = 100 \text{ grams} - 10\% \text{ of } 100 \text{ grams} = 100 - 10 = 90 \text{ grams} \]

### Step 3: Finding the Effective Cost Price for 90 grams
- The Cost Price for 90 grams can be calculated as follows:
\[ \text{CP for 90 grams} = \left(\frac{90}{100}\right) \times 100 = ₹90 \]

### Step 4: Calculating the Profit
- Now, we can calculate the profit made by the shopkeeper when he sells 90 grams for ₹110:
\[ \text{Profit} = SP - CP = 110 - 90 = ₹20 \]

### Step 5: Finding the Effective Profit Percentage
- The profit percentage can be calculated using the formula:
\[ \text{Profit Percentage} = \left(\frac{\text{Profit}}{\text{CP}}\right) \times 100 = \left(\frac{20}{90}\right) \times 100 \]
\[ = \frac{2000}{90} \approx 22.22\% \]

### Final Answer
The effective profit percentage of the shopkeeper is approximately **22.22%**.

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