用简便方法计算(1)678+(354+322)(2)283+147+17+1653(3)384-(37+184)(4)2

1个回答

  • 解题思路:(1)根据加法的交换律即可;

    (2)根据加法的交换律和加法的结合律;

    (3)和(4)根据连续减去两个数等于减去两个数的和;

    (5)是用凑整百法,剩下的题目是利用乘法分配律.

    (1)678+354+322

    =678+322+354

    =1000+354

    =1354;

    (2)283+147+17+1653

    =283+17+(147+1653)

    =300+1800

    =2100;

    (3)384-(37+184)

    =384-(184+37)

    =384-184-37

    =200-37

    =163;

    (4)2904-1327-173

    =2904-(1327+173)

    =2904-1500

    =1404;

    (5)653-197

    =653-200+3

    =453+3

    =456;

    (6)125×17-125

    =125×(17-1)

    =125×16

    =125×8×2

    =1000×2

    =2000;

    (7)235×99

    =235×(100-1)

    =235×100-235×1

    =23500-235

    =23265;

    (8)(1300-520)÷13

    =1300÷13-520÷13

    =100-40

    =60;

    (9)67×21+18×21+85×79

    =21×(67+18)+85×79

    =21×85+85×79

    =85×(21+79)

    =85×100

    =8500;

    (10)222222×999999

    =222222×(1000000-1)

    =222222×1000000-222222×1

    =222222000000-222222

    =222221777778.

    点评:

    本题考点: 运算定律与简便运算.

    考点点评: 解答此题的关键是,根据题目特点,合理利用所学过的运算定律,让计算简便.