Explanation:

- The marked price of each item is Rs 300. For every three items bought, one is free, which means you get 4 items for the price of 3.

- If Ramesh paid Rs 18,000 post-discount, let's calculate:

- First, for every 4 items, he pays for 3, so he effectively buys 4 items at the price of 3.

- Without any offers, 4 items would be Rs 1,200 (4 x Rs 300).

- With the scheme, he buys 4 items for Rs 900 (3 x Rs 300).

- Hence, the effective per item price becomes Rs 900/4 = Rs 225.

- Ramesh's actual buying price without offers = Rs 18,000 / (0.90) = Rs 20,000 (since he got an extra 10% discount with his purchase higher than Rs 10,000).

- Total items purchased at scheme price = Rs 20,000 / Rs 225 = approximately 88.89 items or 89 items.

- Without any concession, 89 items would have cost = Rs 26,700 (89 x Rs 300).

- Effective discount = \( (\text{Marked Price} - \text{Amount Paid}) / \text{Marked Price} \times 100 \% \).

- Calculated effective discount = ((Rs 26,700 - Rs 18,000) / Rs 26,700) x 100% = ~32.584, which rounds to 32.5%.

- Correct Answer: Option 3 – 32.5%.