$M_1 D_1 = M_2 D_2 \Rightarrow 10 imes 20 = 20 imes D_2 \Rightarrow D_2 = 10$.
$M_1 D_1 = M_2 D_2 \Rightarrow 10 imes 20 = 20 imes D_2 \Rightarrow D_2 = 10$।