解题思路:(1)利用加法交换律简算;
(2)(7)(11)(15)(16)利用乘法分配律简算;
(3)(14)(18)利用减法的性质简算;
(4)(5)把32拆成8×4利用乘法交换律与结合律简算;
(6)(13)利用除法的性质简算;
(8)(10)(17)(19)(20)利用加法交换律与结合律简算;
(9)利用乘法交换律简算;
(12)把44拆成4×11,利用乘法交换律与结合律简算.
(1)68+57+32
=68+32+57
=100+57
=157;
(2)202×15
=(200+2)×15
=200×15+2×15
=3030;
(3)23.57-13.44-9.56
=23.57-(13.44+9.56)
=23.57-23
=0.57;
(4)32×125
=4×(8×125)
=4×1000
=4000;
(5)32×125×5
=4×5×(8×125)
=20000;
(6)1120÷14÷8
=1120÷(14×8)
=1120÷112
=10;
(7)68×34-68×24
=68×(34-24)
=68×10
=680;
(8)36.6+25.8+36.6-25.8
=36.6+36.6+(25.8-25.8)
=73.2;
(9)25×17×4
=25×4×17
=1700;
(10)576+68+124+32
=576+124+(32+68)
=700+100
=800;
(11)82×43+18×43
=(82+18)×43
=100×43
=4300;
(12)25×44
=25×4×11
=1100;
(13)72000÷25÷4
=72000÷(25×4)
=72000÷100
=720;
(14)326-168-132
=326-(168+132)
=326-300
=26;
(15)196×99+196
=196×(99+1)
=196×100
=19600;
(16)98×24-98×14
=98×(24-14)
=98×10
=980;
(17)2.95+23.47+5.05+6.53
=(2.95+5.05)+(6.53+23.47)
=8+30
=38;
(18)7.24-(3.68+1.24)
=7.24-1.24-3.68
=6-3.68
=2.32;
(19)25.38+19.52+34.62
=25.38+34.62+19.52
=60+19.52
=79.52;
(20)3.7+6.3+3.7-6.3
=3.7+3.7+(6.3-6.3)
=7.4.
点评:
本题考点: 运算定律与简便运算.
考点点评: 简算注意抓住数字和运算符号的特点,选用适当的方法以及运算定律简算.