29×42≈30×40=1200,
29×42=1218,
167×42≈160×40=6400,
167×42=6847,
405×22≈400×20=8000;
405×22=8910;
故答案为:42,40,1218;41,40,6847,22,20,8910.
29×42≈30×40=1200,
29×42=1218,
167×42≈160×40=6400,
167×42=6847,
405×22≈400×20=8000;
405×22=8910;
故答案为:42,40,1218;41,40,6847,22,20,8910.