Dans le dessin ci-dessous, détermine le poids d'un triangle sachant que la balance est équilibrée (les masses sont exprimées en grammes): \begin{center} \begin{pspicture}(-4,0.5)(4,2.5) \psline[linewidth=0.05cm]{*-*}(-2.25,0.5)(2.25,0.5) \psline[linewidth=0.05cm]{*-}(2.25,0.5)(2.25,1) \psline[linewidth=0.05cm]{*-}(-2.25,0.5)(-2.25,1) \psline[linewidth=0.05cm](-3.75,1.5)(-3.5,1)(-1,1)(-0.75,1.5) \psline[linewidth=0.05cm](0.75,1.5)(1,1)(3.5,1)(3.75,1.5) \psline[linewidth=0.05cm]{*->}(0,0.5)(0,2) \multips(-3.4,1)(0.5,0){3}{\pspolygon*(0,0)(0.5,0)(0.25,0.5)} \multips(1.05,1)(0.5,0){2}{\pspolygon*(0,0)(0.5,0)(0.25,0.5)} \multips(-3.15,1.5)(0.5,0){2}{\pspolygon*(0,0)(0.5,0)(0.25,0.5)} \pspolygon(-1.1,1)(-1.7,1)(-1.7,1.8)(-1.1,1.8)\psellipse(-1.4,1.9)(0.12,0.1) \pspolygon(2.2,1)(2.85,1)(2.85,1.9)(2.2,1.9)\psellipse(2.525,2)(0.12,0.1) \pspolygon(2.95,1)(3.45,1)(3.45,1.6)(2.95,1.6)\psellipse(3.2,1.7)(0.12,0.1) \uput[90](-1.4,1.2){\scriptsize{400}} \uput[90](2.525,1.2){\scriptsize{500}} \uput[90](3.2,1.1){\scriptsize{275}} \end{pspicture} \end{center}