You receive a $ 10,000 check from your grandparents for graduation. You decide to save it toward a down payment on a house. You invest it earning 10% per year and you think you will need to have $ 20,000 saved for the down payment. How long will it be before the $ 10,000 has grown to $ 20,000?

To double the money you received from your grandparents, it will take?