He saves 150,000*.1=$<<150000*.1=15000>>15,000 per year

He needs 450,000*.2=$<<450000*.2=90000>>90,000

So he needs to save for 90,000/15,000=<<90000/15000=6>>6 years

# Answer

6
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
Mike is saving up to buy a house.  He puts away 10% of his $150,000 a year salary.  He needs to save up 20% of the cost of a $450,000 house for a downpayment.  How long will it take?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
6
Mike is saving up to buy a house.  He puts away 10% of his $150,000 a year salary.  He needs to save up 20% of the cost of a $450,000 house for a downpayment.  How long will it take?
train