If Juan takes 4 hours to move from his office to grab lunch, moving from his office and back takes 2*4=<<4*2=8>>8 hours.
The time Juan takes to grab his lunch from his office and back is half the time he takes to read a book, meaning he reads a book in 8*2=<<8*2=16>>16 hours.
If he has a 4000-page book, he will read 4000/16=<<4000/16=250>>250 pages in an hour.
#### 250