-   He got profit ⇒ profit % = 15/10 x 12/12 = 1.5 ⇒ 50%.

To calculate the percentage of profit made by John, we need to first determine the cost price (CP) of each apple and the selling price (SP) of each apple.

Given:

John bought 15 apples for Rs. 10, therefore, CP of each apple = Rs. 10/15 = Rs. 0.67

John sold 12 apples for Rs. 12, therefore, SP of each apple = Rs. 12/12 = Rs. 1

Now, we can calculate the profit made by John using the formula:

Profit = SP - CP

Profit = Rs. 1 - Rs. 0.67 = Rs. 0.33

Therefore, John made a profit of Rs. 0.33 on each apple.

To calculate the percentage of profit, we use the formula:

Profit percentage = (Profit/CP) * 100

Profit percentage = (0.33/0.67) * 100 = 49.25 ≈ 50%

Therefore, the correct answer is option A, which is 50%.

Explanation of terms and formulas used:

1. Cost Price (CP): The price at which an article is purchased is known as its cost price.
2. Selling Price (SP): The price at which an article is sold is known as its selling price.
3. Profit: The difference between the selling price and the cost price is known as the profit.
4. Profit percentage: The percentage of profit is the profit expressed as a percentage of the cost price.
5. Formula for profit: Profit = SP - CP
6. Formula for profit percentage: Profit percentage = (Profit/CP) * 100
7. The percentage of profit can be calculated only when the cost price and selling price are known.

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