#### Answer

262 ft

#### Work Step by Step

Multiply to find the total length of pipe on hand for each size, then sum to find the total length of pipe on hand.
$3\times12=\overset136$
$8\times8=\ \ 64$
$9\times10=90$
$12\times6=\underline{72}$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 262$