At the end of his first week, Brian now has doubled his initial time of 10 seconds to 10*2=<<10*2=20>>20 seconds

At the end of his second week, Brian doubled the previous week's time of 20 seconds to 20*2=<<20*2=40>>40 seconds

At the end of his third week of practice, Brian adds another 50% of 40 seconds to his time so 40*.5= <<40*.5=20>>20 seconds added

Having added 20 seconds to his time from his second week, Brian can now hold his breath for 40+20= <<20+40=60>>60 seconds

# Answer

60
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
Brian can only hold his breath underwater for 10 seconds.  He wants to get better, so he starts practicing.  After a week, he's doubled the amount of time he can do it.  After another week, he's doubled it again from the previous week.  The final week, he's increased it by 50% from the previous week.  How long can Brian hold his breath for now?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
60
Brian can only hold his breath underwater for 10 seconds.  He wants to get better, so he starts practicing.  After a week, he's doubled the amount of time he can do it.  After another week, he's doubled it again from the previous week.  The final week, he's increased it by 50% from the previous week.  How long can Brian hold his breath for now?
train