You graduate and receive a $$$$4$ comma $000$ cheque from your grandparents. You decide to save it toward a down payment on a house. You invest it earning $10\%$ per$$ year, and you think you will need to have $$$$8$ comma $000$ saved for the down payment. How long will it be before the $$$$4$ comma $000$ has grown to $$$$8$ comma $000?$

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Part $1$

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

$$

enter your response here years. $($Round to one decimal$$ place.$)$