Soln = for chaing bolting

An=(b-ndo)8

=(210-4 X 18)8

An=1104 mm$^{2}$

For zig zag bolting

1) along path AB & FG (2 holes) net area will be

An=$(b-nda)t+(\frac{\sum p^{2}}{4g})$

=(210 X 2 X 18)8+0

=1392 mm$^{2}$

2) Along path cnf (three holes)

An=(h-nda) X t+$\frac{\sum p^{2}}{4g}$

=(210-3 X18)X8+0

An=$1248mm^{2}$

3) …