考点:整数四则混合运算,运算定律与简便运算
专题:运算顺序及法则,运算定律及简算
分析:(1)(2)(3)利用加法交换律与结合律简算;
(4)(5)(6)利用减法的性质简算;
(7)(8)利用凑整计算;
(9)利用加法交换律与减法的性质简算.
解答:
解:(1)15+24+36+45
=15+45+(24+36)
=60+60
=120;
(2)782+324+218
=782+218+324
=1000+324
=1324;
(3)622+(497+578)
=622+578+497
=1200+497
=1697;
(4)432-123-77
=432-(123+77)
=432-200
=232;
(5)435-(135+189)
=435-135-189
=300-189
=111;
(6)435-49-11-40
=435-(49+11+40)
=435-100
=235;
(7)800-405
=800-400-5
=400-5
=395;
(8)316-98
=316-100+2
=216+2
=218;
(9)175-57-43+25
=175+25-(57+43)
=200-100
=100.
点评:整数混合运算的关键是抓住运算顺序,正确按运算顺序计算,适当利用运算定律简算.