計(jì)算下面各題:(能簡(jiǎn)算的要簡(jiǎn)算)
6.7+25+3.3+75
103×12
14.85-(4.85+2.5)
15×99+15
9.14-1.43-4.57
2000÷125÷8.
解:(1)6.7+25+3.3+75
=(6.7+3.3)+(25+75),
=10+100,
=110;
(2)103×12
=(100+3)×12,
=100×12+3×12,
=1200+36,
=1236;
(3)14.85-(4.85+2.5)
=14.85-4.85-2.5,
=10-2.5,
=7.5;
(4)15×99+15
=(99+1)×15,
=100×15,
=1500;
(5)9.14-1.43-4.57
=9.14-(1.43+4.57),
=9.14-6,
=3.14;
(6)2000÷125÷8
=2000÷(125×8),
=2000÷1000,
=2.
分析:算式(1)可根據(jù)加法交換律及結(jié)合律進(jìn)行計(jì)算;
算式(2)可將式中103拆分為100+3后再根據(jù)乘法分配律計(jì)算;
算式(3)可根據(jù)一個(gè)數(shù)減兩個(gè)數(shù)的和,等于用這個(gè)數(shù)分別減去這兩個(gè)數(shù)的減法性質(zhì)進(jìn)行計(jì)算;
算式(4)可根據(jù)乘法分配律進(jìn)行計(jì)算;
算式(5)可根據(jù)一個(gè)數(shù)減兩個(gè)數(shù)等于用這個(gè)數(shù)減去這兩個(gè)數(shù)的和減法性質(zhì)進(jìn)行計(jì)算;
算式(6)可根據(jù)一個(gè)數(shù)除以兩個(gè)數(shù)等于用這個(gè)數(shù)除以這兩個(gè)數(shù)的積的除法性質(zhì)進(jìn)行計(jì)算.
點(diǎn)評(píng):完成本題要細(xì)心分析式中數(shù)據(jù)的特點(diǎn)及內(nèi)在聯(lián)系,利用合適的方法進(jìn)行計(jì)算.