###Human: Betty has 20 books, and her sister has 1/4 times more books than Betty. What's the total number of books the two have?, ### Assistant: Betty's sister has 1/4 * 20 books = 5 more books.
The total number of books Betty's sister has is 20 books + 5 books = 25 books
The total number of books the two have is 25 books + 20 books = 45 books 
 So the answer is :  45