Rounded book

When the book was rounded as shown in Fig. 1 and looked at from right above, it was seen as shown in Fig. 2.

The figure of Fig. 2 is made of a straight line and a semicircle.

In this case, how many times of the thickness of the book is the length of x of Fig. 2?

The answer should be rounded off a 2nd decimal place and should find it to the 1st decimal place.

Answer