What are the prices of...

[thehammer]

Which one is correct?

1- What are the price(s) of 1 kg of rice and 1 kg of wheat?

2- The price(s) of 1 kg of rice and 1 kg of of wheat is/are 50 rupees and 40 rupees .

 

[Tarheel]

Abe: What's the cost of one kg of rice and one kg of wheat?
Bob: 90 rupees.

Abe wants to know what it's going to cost him to buy both items, so that is the question he asks. However, you could also say, "What are the prices of X and Y (combined)?"

 

[Barque]

What are the price(s) of 1 kg of rice and 1 kg of wheat?

In actual conversation you're more likely to hear:

How much is a kilo of rice and a kilo of wheat? How much are rice and wheat per kilo?
Rice's 50 and wheat's 40/Rice costs 50 and wheat 40.

The person answering doesn't need to repeat "a kilo of"