Step 1: Treat each couple as a block.
If each husband must sit next to his wife, consider each couple as a single block. There are $3$ blocks to arrange around a circle. For circular arrangements (only rotations considered identical), the number of ways to arrange $3$ distinct blocks is $(3-1)! = 2$.
Step 2: Arrange within each block.
Inside a couple's block, the two people can sit as $(H,W)$ or $(W,H)$, i.e., $2$ ways per block.
Hence internal arrangements contribute a factor of $2^3 = 8$.
Step 3: Multiply choices.
Total valid seatings $= (3-1)! \times 2^3 = 2 \times 8 = 16$.
\[
\boxed{16}
\]
Let R = {(1, 2), (2, 3), (3, 3)}} be a relation defined on the set \( \{1, 2, 3, 4\} \). Then the minimum number of elements needed to be added in \( R \) so that \( R \) becomes an equivalence relation, is:
Two soils of permeabilities \( k_1 \) and \( k_2 \) are placed in a horizontal flow apparatus, as shown in the figure. For Soil 1, \( L_1 = 50 \, {cm} \), and \( k_1 = 0.055 \, {cm/s} \); for Soil 2, \( L_2 = 30 \, {cm} \), and \( k_2 = 0.035 \, {cm/s} \). The cross-sectional area of the horizontal pipe is 100 cm², and the head difference (\( \Delta h \)) is 150 cm. The discharge (in cm³/s) through the soils is ........ (rounded off to 2 decimal places).

The most suitable test for measuring the permeability of clayey soils in the laboratory is ___________.
Consider the beam ACDEB given in the figure. Which of the following statements is/are correct:

The figures, I, II, and III are parts of a sequence. Which one of the following options comes next in the sequence as IV?
