Brian begins by watching a 4-minute video, and since the second video is twice as long that means the second video is 4*2= <<4*2=8>>8 minutes.

The first two videos combined therefore for a 4+8=<<4+8=12>>12 minute run time.

Since the third video is twice as long as the first two videos put together, that means it is 12*2=<<12*2=24>>24 minutes in length.

The total length of time spent is therefore 24+12= <<24+12=36>>36 minutes

# Answer

36
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
Brian loves watching animal videos online.  He watches a 4-minute video of cats.  He then watches a video twice as long as the cat video involving dogs.  He finishes up his video watching for the day by watching a video on gorillas that's twice as long as the previous two videos combined.  How many minutes does Brian spend watching animal videos?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
36
Brian loves watching animal videos online.  He watches a 4-minute video of cats.  He then watches a video twice as long as the cat video involving dogs.  He finishes up his video watching for the day by watching a video on gorillas that's twice as long as the previous two videos combined.  How many minutes does Brian spend watching animal videos?
train