An explosion in a rigid pipe results in two small pieces of material being ejected in opposite directions.$$ If the piece coming out the right end has a mass of $7\mathrm{.}91$ g and moves at a speed of $8\mathrm{.}49$ m$/$s$,$ what is the speed $($in m$/$s$)$ of the $7\mathrm{.}5$ g left piece?$($Be sure to enter your answer to at least two decimal places to avoid rounding error.$)$