7.
面积为\(S\)的平面凸四边形的第\(i\)条边的边长记为\(a_{i}(i=1,2,3,4)\),此四边形内任一点\(P\)到第\(i\)条边的距离为\(h_{i}(i=1,2,3,4)\),若\( \dfrac {a_{1}}{1}= \dfrac {a_{2}}{2}= \dfrac {a_{3}}{3}= \dfrac {a_{4}}{4}=k\),则\(h_{1}+2h_{2}+3h_{3}+4h_{4}= \dfrac {2s}{k}\);根据以上性质,体积为\(V\)的三棱锥的第\(i\)个面的面积记为\(S_{i}(i=1,2,3,4)\),此三棱锥内任一点\(Q\)到第\(i\)个面的距离记为\(H_{i}(i=1,2,3,4)\),若\( \dfrac {S_{1}}{1}= \dfrac {S_{2}}{2}= \dfrac {S_{3}}{3}= \dfrac {S_{4}}{4}=k\),则\(H_{1}+2H_{2}+3H_{3}+4H_{4}=(\) \()\)