A vegetable seller bought 10 dozens of potatoes for ₹120, another 5 dozens for ₹50 and another 5 dozens for ₹30. He sold the potatoes for ₹9 a dozen. How much discount did he overall offer?

10%

Vegetable seller bought 10 dozens of potatoes for ₹120

He again bought 5 dozens of potatoes for ₹50

He again bought 5 dozens of potatoes for ₹30

Cost price of 20 dozens of potatoes = 120 + 50 + 30 = Rs. 200

Hence, cost price of 1 dozen of potatoes = \(\frac{200}{20}\) = Rs. 10

Now, selling price of 1 dozen of potatoes = Rs. 9

Discount% = 1 × \(\frac{100}{10}\) = 10%