4人10天修路840米。照这样的速度,20人修路4200米,需要多少天?5[(~+v'\*n4_2?2F(d)h'T(u,t*M
算式:提示0^/G1^1]1v5[(~+v'\*n4_2?2F(d)h'T(u,t*M
答:需要+R1C0u.F-h8u2z;}:A3r'Z-x:u4u0n;Z;G天。5[(~+v'\*n4_2?2F(d)h'T(u,t*M