Yeah Peter is right. I also want to note that "chia" can also mean "divide". Like "sáu chia hai là ba" = "six divided by two is three". You really are dividing your own food in order to share it, wouldn't you agree? Maybe that will help you with remembering some vocab?
Yes. This is very helpful. I wish DL provided more information on other uses of the same word, since it would help us to remember