1. 29×10+29×8=(______+______)×______.78×17×87=______×______×______
(1)29×10+29×8=( 10+8)×29=18×29=4;(2)78×17×87=78×87×17=1×17=17.故答案为:10,8,29;78,87,17.
2. ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
设列车长X米
(350+2X)/20=X/6
X=262.5
列车长262.5米
3. ------------------------------------------------------------------------------------------
1、纱布擦拭目镜。
2、调节反光镜,对光。
3、同时转动细准焦螺旋
4. a×6+6×15=________×(________+________).
6 a 15
a×6+6×15=6×(a+15);
故答案为:6,a,15.
5. 21×9=______321×9=______4321×9=______54321×9=____________×9=____________×9=____________×9=__
21×9=189,321×9=2889,4321×9=38889,54321×9=488889,654321×9=5888889,7654321×9=68888889,87654321×9=788888889.故答案为:189,2889,38889,488889,654321,5888889,7654321,68888889,87654321,788888889.
6. 40÷5=80÷______=(40×4)÷(5×______)=______÷______.
40÷5=80÷10=(40×4)÷(5×4)=8÷1.
鼓捣案为:10;4;8;1.
7. 850÷5÷2=850÷(______×______)=850÷______=______.
850÷5÷2=850÷(5×2)=850÷10=85.
故答案为:5,2,10,85.
8. 102×35=(______+______)×______=______×______+______×______.
102×35
=(100+2)×35
=100×35+2×35
=3500+70
=3570.
故答案为:100;2;35;100;35;2;35.