Richard can read 1/4 of a book in 2/5 of an hour. At this rate, how much can Richard read in one hour?

If he reads 1/4 of a book in 2/5 of an hour

he will read 0.625 of a book in an hour, or 5/8 of a book.

solve it with a proportion

1/4 of a book : 2/5h = X : 1h

X = (1/4) / (2/5) = 5/8

0.375 of a book in an hour