buy 2kg of peanuts get 300 g free
tom buys 4kg of peanuts how many grams of peanuts does he get in all?
If Tom buys 4kg of peanuts, he will get 300g of peanuts for each 2kg.
Therefore, Tom will get 300g + 300g = <<300+300=600>>600g free.
So in total, Tom will get 4kg + 600g = <<4+600=604>>604g of peanuts. Answer: \boxed{604}.