<human>:  Studying for her test, Mitchell had read ten chapters of a book before 4 o'clock. When it clocked 4, Mitchell had read 20 pages of the 11th chapter of the book she was studying from. After 4 o'clock, she didn't read the remaining pages of chapter eleven but proceeded and read 2 more chapters of the book. If each chapter in the book had 40 pages, calculate the total number of pages that Mitchell had read altogether?
<bot>: How many pages did Mitchell read from the first ten chapters? ** Since each chapter of the book has 40 pages, Mitchell had read 10*40 = <<10*40=400>>400 pages from the first ten chapters.
How many pages did Mitchell read altogether? ** After reading 20 pages of the eleventh chapter, the total number of pages that Mitchell had read is 400+20 = <<400+20=420>>420
How many pages did Mitchell read from the next two chapters? ** The next two chapters that she read had 2*40 = <<2*40=80>>80 pages.
How many pages did Mitchell read altogether? ** In total, Mitchell read 420+80 = <<420+80=500>>500 pages of the book that day.
#### 500