递等式计算(能简便的要简便计算):
6.01-1.9+4.99-2.1
0.25×32×12.5
0.65×64-65×0.54
90÷(3.6-1.8)
52+6.5+26×0.37
0.36÷[(6.1-4.6)×0.8].
解:(1)6.01-1.9+4.99-2.1,
=(6.01+4.99)-(1.9+2.1),
=11-4,
=7;
(2)0.25×32×12.5,
=(0.25×4)×(8×12.5),
=1×100,
=100;
(3)0.65×64-65×0.54,
=0.65×64-0.65×54,
=0.65×(64-54),
=0.65×10,
=6.5;
(4)90÷(3.6-1.8),
=90÷1.8,
=50;
(5)52+6.5+26×0.37,
=58.5+9.62,
=68.12;
(6)0.36÷[(6.1-4.6)×0.8],
=0.36÷[1.5×0.8],
=0.36÷1.2,
=0.3.
分析:(1)运用加法交换律与结合律以及减法的性质简算;
(2)把32看作4×8,运用乘法结合律简算;
(3)原式变为0.65×64-0.65×54,运用乘法分配律简算;
(4)先算括号内的,再算括号外的;
(5)先算乘法,再算加法;
(6)先算小括号内的,再算中括号内的,最后算括号外的.
点评:此题小数的四则混合运算,注意运算顺序和运算法则,灵活运用所学的运算定律进行简便计算.