Theory:

Meha went to a supermarket to buy some groceries for her family. Let's see a conversation between Meha and shop keeper.
 
Shop keeper: Welcome mam! How can I help you?
 
Meha: I need some groceries.
 
Shop keeper: Yes, tell me, what do you want?
 
Meha: I want \(2 \ kg\) tomatoes, \(1 \ kg\) onion, \(500 \ grams\) of potato and \(250 \ grams\) of chillies.
 
Shop keeper: Here is yours mam. Do you want anything else other than this?
 
Meha: No, that's it. I need a bill along with the groceries.
 
Shop keeper: Sure mam. Here is the bill of your purchase.
 
bill.png
 
Meha: Thank you so much.
 
Shop keeper: Welcome mam.
 
In the bill, as mentioned above, there are two types of quantities given. One is kilogram, and the other is gram. Same units only can be added. So, that kilograms and grams added separately.
 
Important!
1. Measurement with the same units only can be added/subtracted.
 
2. Measurement with different units should be converted to the same units and then add or subtract.