In a certain warehouse, there are $1335$ boxes, each containing $39$ books.

Melvin's boss orders him to unpack all the books and repack them so that there are $40$ books in each box. After packing as many such boxes as possible, Melvin has how many books left over?
To find the total number of books, I can multiply the number of boxes by the number of books per box: $1335 \times 39 = 52065$. To find the number for boxes for $40$ books each, I can divide the total number of books by $40$: $\frac{52065}{40} = 1301.625$. This means I can fill $1301$ boxes completely, and have some books left over. To find the number of books left over, I can multiply the fractional part of the previous quotient by $40$: $0.625 \times 40 = 25$. Therefore, Melvin has $25$ books left over after packing as many $40$-book boxes as possible.

