What is the formula for the weight of a fluid block?

[werson tan]

Homework Statement

why the formula of weight of fluid block is given by the formula of ρg[ (R^2) - pi(R^2) ] 1?

what does the 1m mean here ?
shouldn't it = ρg (pi) (R^2) h ?
2. Homework Equations

The Attempt at a Solution

 

[BvU]

It's a square minus a quarter circle. $W$ is the weight of 1 m length (i.e. into the paper) of the area shaded grey in the right picture in Fig 3-36.