1 doi cong nhan co 120 nguoi dap 1 doan duong dai 4 km, Ban chi huy tinh rang de hoan thanh cong viec dung thi moi nguoi phai lam 8 gio moi ngay . Truoc khi khoi cong , thi them 30 nguoi va phai dap them 1 km duong nua . Hoi de hoan thanh dung ke hoach thi moi nguoi phai lam bao nhieu gio moi ngay ?