计算(写出主要过程,能简便的要用简便算法)39×2+19845.78+45.78×99 7 8 ÷9× 3 5

2025-04-16 06:47:48
推荐回答(1个)
回答1:

(1)39×2+198,
=(40-1)×2+(200-2),
=40×2-2+200-2,
=280-4,
=276;
(2)45.78+45.78×99,
=(1+99)×45.78,
=100×45.78,
=4578;
(3)
7
8
÷9×
3
5
÷
35
72

=
7
8
×
1
9
×
3
5
×
72
35

=
3
25

(4)3.6-2.8+7.4-7.2,
=(3.6+7.4)-(2.8+7.2),
=10-10,
=0.