I am a green card holder of USA, and I am travelling to India. While leaving India for the US, I want to carry dollars. What is the limit that I can carry to US, being a green card holder?
As far as the US is concerned, there is no limit but if have more than USD 10000 with you, you should report it to the US customs.
India has strict restrictions on travel with Indian Rupees but not on foreign currency. There is a mandatory declaration as well, see Is it really forbidden to cross the Indian border with Indian rupee?
The amount of US dollars (cash) you can bring into the USA is set by your airline - usually 23kg per checked bag, 7kg carry-on. If it's all in hundreds that's ..... a lot.
You will need to declare to US customs (and most other countries for that matter) if you have cash or cash equivalents (gold, bearer cheques etc.) totalling $10,000 or more. That's the sum of your USD, Rupees, Euros etc. It's not complicated, just where did you get it and why it's in cash. Bring the withdrawl slip from the bank, show them your green card, SSN, and US bank cash card and it should take 5 minutes. People regularly return to Canada with a stack of US cash from Las Vegas. Show the customs staff the casino payslip and a photo of the 3 cherries on the slot machine and the reply is usually "Congratulations! Have a nice day, eh."
However, it's a lot safer to just wire transfer the funds. $40 for an international wire transfer and the money appears 1-2 days later. Or if your Indian bank cash card has a Plus logo on the back it will very likely work in most US cash machines.