Cost of the vegetable is Rs 100/kg and he’s earning a profit of 20%.

His profit is Rs 20/kg

His Selling Price will be Rs 120/Kg.

But as he is selling 900 grams as 1kg. His profit will be changed as follows:

As we know 1kg = 1000grams = Rs 100

Therefore, 900g = Rs 90

So, the new cost price= Rs 90

But, new Selling price = Rs 120

Hence, he is earning Rs 30 on 900 grams.

=> His actual profit % = Rs30/Rs90 *100

= 33.33%