Ответ:
\(709\cdot23=709\cdot(20+3)=14\,180+2\,127=16\,307\).
\(1360\cdot24=1360\cdot(20+4)=27\,200+5\,440=32\,640\).
\(640\cdot19=640\cdot(20-1)=12\,800-640=12\,160\).
\(3914\cdot38=3914\cdot(30+8)=117\,420+31\,312=148\,732\).
Ответ: 16 307; 32 640; 12 160; 148 732.
