<human>:  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?
<bot>: How long can Brian hold his breath for after the first week? ** 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
How long can Brian hold his breath for after the second week? ** 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
How long can Brian hold his breath for after the third week? ** 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
How long can Brian hold his breath for now? ** 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
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