#### Answer

90$\frac{1}{2}$ in

#### Work Step by Step

Given - the saw blade removes an additional $\frac{1}{8}$ in of wood each time a board is cut
We need to find the shortest length of the board that allow us to cut 5 pieces each of length 18 in
= 5 x 18 in + 4 x $\frac{1}{8}$ in
= 90 + $\frac{1}{2}$ in
=$\frac{180}{2}$ in + $\frac{1}{2}$ in
= $\frac{181}{2}$ in
=90$\frac{1}{2}$ in